Abstract Book(pdf format)

PREFACE

The National Laser Symposium (NLS) is now an established scientific event, eagerly awaitedby Scientists and Engineers, working in the exciting field of Lasers and their applications inIndia. The present one is the “Sixth” in the series. The previous one, the “Fifth”, was held lastyear at VIT, Vellore. This year, the Symposium is being organized at Raja Ramanna Centre forAdvanced Technology (RRCAT). RRCAT is an R&D unit of DAE, actively involved in thedevelopment of Accelerators and Lasers. This year also happens to be the “BARC GoldenJubilee Year”. The symposium is sponsored by BRNS (Board of Research in Nuclear Sciences)of DAE and is being organized in collaboration with Indian Laser Association (ILA).

The Indian Laser Association plays a major role in the organization of the Symposium. It organizesan exhibition of “Laser related products” during the Symposium. This year, about thirty vendorsare expected to participate in the exhibition. Just prior to the Symposium, on December 3rd and4th, ILA has arranged two Short Courses, for the benefit of students and young researchers.About hundred participants have attended these short courses. Majority of these participants arealso attending the Symposium.

This year, the theme for the Symposium is “Semiconductor Lasers”. This is an important areaof research and technology, in which India has made considerable progress. The technical sessionson the first day are devoted to various aspects of Semiconductor Laser development like:semiconductor material growth, device design, fabrication, packaging etc. Prof. B.M.Arora(TIFR, Mumbai), who is an internationally known scientist active in the area of “SemiconductorLasers” will be delivering the “Keynote Address” at the Symposium.

The technical sessions, spread over all the four days of the Symposium, will feature twenty-sixinvited talks, covering various aspects of Lasers and their applications. All the 240 contributedpapers, accepted after scrutiny, will be presented as poster papers. The poster sessions are beingheld on the first three days of the Symposium. On the last day, there is a session for thesispresentation. This session promises to be a lively one with ten thesis presentations. The concludingsession on the last day, features presentation of awards, for the “Best Poster” and “Best Thesis”.ILA will give these awards.

The “Abstract Book” contains short abstracts of the posters, invited talks and the theses. The“Extended Abstracts” of the posters and the thesis summaries have been published in a “CD”,which is accompanying this abstract book.

ILA is bringing out a special issue of “KIRAN” (Bulletin of the Indian Laser Association), topublish the invited talks of the Symposium. This is being done for the benefit of the participantsfor the first time and ILA deserves a special credit for this effort.

A few special sessions have been arranged in the evenings. These include a session on “Patents”and “Technology transfer”. We hope that these topics would be of interest to the students,researchers and industrial participants. However the highlight of the Symposium is the “PlenarySession”, in which Prof. Govind Swarup (NCRA, Pune) will share his views and experience onthe development of Giant Metrewave Radio Telescope (GMRT) with the participants. We alsohope that the participants will enjoy the “Cultural Programmes”.

The above relates to the organization aspects of the Symposium. However the real outcome andsuccess of the Symposium depends on the level of participation. We sincerely hope that therewill be lively discussions and interactions among the participants in all the sessions of theSymposium, and the Symposium will lead to innovation and quality in our future scientificworks, and act as a catalyst for increased interaction and cooperation among the delegates.

It is our pleasant duty now to thank all those, who have made this Symposium possible. We aregrateful to Dr. V.C. Sahni (Director, RRCAT), who has provided his guidance and help at allstages of organization of this Symposium. We are grateful to the numerous colleagues, whosetimely and silent help in the organization of the varied activities related to this Symposium,deserves special mention and acknowledgement. We thank the speakers for accepting ourinvitation and preparing interesting talks on the latest developments in their fields. We thank themembers of the “National Advisory Committee” and “Symposium Organizing Committee” fortheir keen interest in the Symposium and their valuable suggestions.

We take this opportunity to welcome all the delegates. Thank you very much for attending thisSymposium and making it a success. We sincerely hope to get your association and patronagein future.

U. Nundy Tapas GanguliConvenor, NLS-6 Secretary, NLS-6

:: CONTENTS ::

Page No.

I. Programme Schedule 5-8

II. Invited Talks 9-40

III. Contributory Papers :

Topics :

1) Physics and Technology of Lasers 43

2) Lasers in Nuclear Science and Technology 50

3) Semiconductor Lasers and Optoelectronic Devices 51

4) Laser Materials: Devices and Components 53

5) Quantum Optics 66

6) Ultrafast Lasers and Applications 67

7) Nonlinear Optics 69

8) Laser Spectroscopy 73

9) Laser Plasma Interaction 80

10) Lasers in Industry and Defence 84

11) Lasers in Chemistry, Biology and Medicine 86

12) Laser based Instrumentation 91

13) Lasers in Material Science 96

IV. Thesis Abstracts 99-114

V. List of Exhibitors 115

VI. NLS-6 Committees 116-120

VII. Important Phone Numbers 121

VIII. Air Time Table 122

IX. Railway Time Table 123

NLS-6 4

NLS-6 5

SIXTH DAE- BRNSNATIONAL LASER SYMPOSIUM (NLS-6)

December 5-8, 2006

PROGRAM SCHEDULE

Tuesday, 5th December 2006

✦ Session I : Inauguration of Symposium and Exhibition 9:30 to 11:15 Hrs.Welcome and Introductory Speeches 9:30 to 10:00 Hrs.

Keynote address 10:00 to 10:45 Hrs.Prof. B.M. Arora, TIFR, MumbaiProgress in Semiconductor Diode Lasers

Opening of ILA Exhibition and Visit to Stalls 10:45 to 11:15 Hrs.

High Tea - 11:15 to 11:45 Hrs.

✦ Session II : Semiconductor Lasers - I 11:45 to 13:15 Hrs.Prof. Diana Huffaker, Univ. of New Mexico, USAQuantum Dot Lasers

Dr. S.K. Mehta, SSPL, DelhiDevelopment of High Power SQW SCH GaAlAs- GaAs Laser Diodes

Dr. Tarun K. Sharma, RRCAT, IndoreDevelopment of High Power Quantum Well Lasers at RRCAT

Lunch - 13:15 to 14:15 Hrs.

✦ Session III : Semiconductor Lasers - II 14:15 to 15:45 Hrs.Dr. B.R. Singh, CEERI, PilaniHigh Reliability 980 nm pump Lasers for Erbium doped fiber amplifiers

Mr. K.S. Kumar, Optiwave Photonics, HyderabadPackaging of Semiconductor Lasers

Dr. Sudakshina Kundu, West Bengal University of Technology, KolkataDesign of Blue and Blue - Green Lasers

✦ BRNS: 15:45 to 16:00 Hrs.Dr. P.P. Chandrachoodan, BARC, MumbaiMobilisation of collaborative Research Program through BRNS

Tea - 16:00 to 16:15 Hrs.

✦ Session IV : Poster Session - I 16:15 to 18:15 Hrs.Tea - 18:15 to 18:30 Hrs.

✦ Special Session : Plenary Talk 18:30 to 19:30 Hrs.Prof. Govind Swarup, NCRA, PuneNew challenges in the fields of Science and Technology in India: Lessons from the GMRT

✦ Cultural Programme 19:30 to 20:30 Hrs.“Kathak Nritya”, Dr. Suchitra Harmalkar and her troupe

Dinner - 20:30 Hrs.

NLS-6 6

Wednesday 6th December 2006

✦ Session V : Physics and Technology of Lasers - I 09:30 to 11:00 Hrs.

Dr.Anil Kumar, LASTEC, New DelhiDevelopment of High Power Gas Dynamic Lasers

Prof. Victor Tarasenko, Inst. of High Current Electronics, RussiaExcimer Lasers pumped by Discharge and E-beam

Dr. D.J. Biswas, BARC, MumbaiSwitch-less operation of TE Gas Lasers

Tea - 11:00 to 11:30 Hrs.

✦ Session VI : Ultrashort and High Intensity Lasers 11:30 to 13:00 Hrs. and their applications

Dr. K.S.Bindra, RRCAT, IndoreMechanism of Nonlinearity in Semiconductor Doped Glasses

Dr. Ajay K Singh, BARC, MumbaiCoherent control of molecular dynamics with shaped Femtosecond Laser pulses

Dr. Prasad A. Naik, RRCAT, IndoreCoherent XUV radiation from Laser plasma plumes throughhigh order harmonic generation

Lunch - 13:00 to 14:00 Hrs.

✦ Session VII : Lasers in Biology and Medicine 14:00 to 15:30 Hrs.

Dr. Suresh Bhat, NCL, PuneStructure, Dynamics and Rheology of soft materials using Laser light scattering technique

Dr. K. Divakar Rao, RRCAT, IndoreOptical Coherence Tomography

Dr. C. Murli Krishna, MAHE, ManipalApplication of Raman Spectroscopy in cancer management

Tea - 15:30 to 15:45 Hrs.

✦ Session VIII : Poster session - II 15:45 to 17:45 Hrs.

Tea - 17:45 to 18:00 Hrs.

✦ ILA Meeting 18:00 to 19:00 Hrs.

19:15 Hrs. Departure for dinner at Nakharali Dhani

NLS-6 7

Thursday, 7th December 2006

✦ Session IX : Physics and Technology of Lasers - II 09:30 to 11:00 Hrs.

Prof. G.J. Tallents, Univ. of York, UKMeasuring plasma opacity using X-Ray Lasers

Mr. J.K. Mittal, RRCAT, IndoreCopper Vapour Lasers - A review and development at RRCAT

Dr. P.K. Datta, IIT, KharagpurGeneration and Characterization of ultrashort Laser pulse

Tea - 11:00 to 11:30 Hrs.

✦ Session X : Laser Spectroscopy and Quantum Optics 11:30 to 13:00 Hrs.Dr. T.S. Rao, BARC Facility, KalpakkamConfocal Laser Scanning Microscopy in Environmental Biotechnology,Biofilms and Microbial corrosion research

Dr. Harshawardhan Wanare, IIT, KanpurMulticolored atomic coherence

Dr. Andal Narayanan, RRI, BangaloreOptical pumping and Coherence effects in fluorescence from a four level system

Lunch - 13:00 to 14:00 Hrs.

✦ Session XI : Laser Applications in 14:00 to 15:30 Hrs. Nuclear Technology, Industry and Instrumentation

Dr. R..Krishnan, IGCAR, KalpakkamSynthesis and Surface Modification of Ceramic Coatings using Lasers

Mr. Aseem Singh Rawat, BARCLaser based Instruments for flow visualization, speed and distance measurement

Mr. B.N. Upadhyaya, RRCAT, IndoreApplications of High Power Solid State Lasers in Nuclear field

Tea - 15:30 to 15:45 Hrs.

✦ Session XII : Poster Session - III 15:45 to 17:45 Hrs.

Tea - 17:45 to 18:15 Hrs.

✦ Popular Lectures 18:15 to 19:15 Hrs.i) Inevitability of IPR Management in R&D of possible Industrial use

Dr. A.D. Damodaran, (Rtd) Director, CSIR/GOI Regional Res. Lab., Trivandrum

ii) An endeavour to transfer Laser Technology to Industries Dr. A.K. Nath, RRCAT, Indore

✦ Cultural Programme (Local Talents) 19:30 to 20:30 Hrs.

Dinner - 20:30 Hrs.

NLS-6 8

Friday 8th December 2006

✦ Session XIII : Thesis presentations 09:00 to 11:30 Hrs.

Tea - 11:30 to 12:00 Hrs.

✦ Session XIV : Laser Materials 12:00 to 13:00 Hrs.Prof. S.B. Rai, BHU, VaranasiSpectra of doped Laser materials and up conversion Laser systems

Dr. S. Ganesamoorthy, RRCAT, IndoreGrowth of large, device quality NLO crystals by flux growth method

✦ Session XV : Concluding session, Best thesis 13:00 to 13:30 Hrs. and Best poster award presentation

Lunch - 13:30 to 14:30 Hrs.

INVITED TALKS

NLS-6 11

Progress in Semiconductor Diode Lasers

B.M. ARORADept. of Condensed Matter Physics and Materials Science,

T.I.F.R, Mumbai-400 005email : [email protected]

Semiconductor diode lasers have come a long way since their invention in 1962. From simplep-n junction devices operable pulsed at cryogenic temperatures, the diode lasers of today arecomplex structures, which can deliver more than 10W CW power at room temperature as singledevices and kilowatts of power as arrays. They are compact sources, have long life and arepreferred to all other types of lasers wherever they can meet the requirements. Their uses nowencompass communications, information storage, industrial materials processing, environmentmonitoring, medicine, diagnostics, defense,basic research and spectroscopy.

Early breakthrough in the chain of developments of the diode lasers was the emergence ofdouble heterostructure for lowering the threshold current density by optical confinement andcarrier confinement. Introduction of quantum well as a separate confinement layer for the carriersopened up a whole new vista, providing very large freedom of choice in the selection of materialof the active layer and for band structure engineering (strained QWs) which continues to beexplored in various forms. Adding to this, was the whole synergy of methods of synthesis ofmultilayers of III-V semiconductors of controlled thickness and composition by molecular beamepitaxy and metal organic vapour phase epitaxy. Many innovations in laser structures and in thematerials have dominated the field, for example: distributed feedback for single mode devices,vertical cavity surface emitting lasers for high beam quality without lens, dilute nitride GaInNAs/GaInNAsSb quantum well devices for 1.3-1.55 mm on GaAs substrates. Intense experimentationis ongoing for devices based on quantum dots. Introduction of III-nitrides has opened up anotherfield for blue, violet and ultrviolet devices. Thus diode lasers cover a very large wavelengthrange from UV to mid-infrared. Quite apart from these band to band devices, there has beenwhole separate development of lasers based on intersub-band devices, quantum cascade lasers,which reach into the far infrared and teraherz regime.

Acitivities in the area of semiconductor lasers in India have picked up over the past few yearsand the progress has been rapid. There are at least 5 groups which have reached the stage ofsynthesizing materials and fabricating devices in the wavelength range 750-1000 nm based onGaAs substrates. It is now a matter of time when high quality devices approaching state of theart in the laboratories elsewhere will be made in several laboratories here.

In my presentation, I shall try and present an overview of the current status of the developmentsin the diode lasers which gives indication of the directions which we expect to emerge in thiscountry in the near future.

NLS-6 12

Development of High Power SQW SCH GaAlAs-GaAsLaser Diodes

S.K. MEHTASolid State Physics Laboratory,Lucknow Road, Delhi-110054

email : SK_MEHTA/[email protected]

The work done at SSPL on the development of Single Quantum Well Separate ConfinementHetero-Structure (SQW-SCH) laser diode which includes the growth of single quantum wellGaAlAs-GaAs material structure, fabrication of mesa and proton bombarded stripe, packagingof laser diode chips and evaluation of the performance of laser diode is reported. Pulsed laserdiode of peak power up to ~14 watts and continuous wave (CW) laser with power of one watthave been developed. Some of the CW laser diodes have as well been operated up to 1.5 watts.The CW laser diodes so developed have been used to pump solid-state micro-cavity of Nd:YVO

4:KTP for emission of green laser light of wavelength 532 nm.

0.0 0.5 1.0 1.5 2.00

200

400

600

800

1000

1200

1400

16001.5W

Rs=0.3 ohms

dP/dI=993mW/Amp

0.4A

Lig

ht (

mW

)

Current (Amp)0 2 4 6 8 10 12 14 16

0

2

4

6

8

10

12

14

16

Peak Power 14 Watts

0.81A

Ligh

t(W

atts

)

Current(Amp)

NLS-6 13

Development of High Power Quantum Well Lasers at RRCAT

T. K. SHARMA, TAPAS GANGULI, V. K. DIXIT, S. D. SINGH,S. PAL, S. PORWAL, RAVI KUMAR, ALEXANDER KHAKHA, R. JANGIR,

V. KHERAJ1, P. RAWAT

2 and A. K. NATH

Semiconductor Laser Section,Raja Ramanna Centre for Advanced Technology, Indore-452 013

1Applied Physics Department, M.S. University of Baroda, Vadodara-390001

2School of Physics, Vigyan Bhawan, DAVV, Indore-452 017

email: [email protected]

There is an increasing demand for high power quantum well lasers for a variety of applicationsespecially as a pump source in solid state lasers[1,2]. The generation of green, blue and UVradiation by frequency upconversion in solid state lasers is of great importance for variousapplications of lasers e.g. pumping of Ti-Sapphire lasers, replacement of copper vapour laserfor pumping Dye lasers and many other applications. We have recently developed high powerlaser diodes in the wavelength range of 740 nm to 1000 nm. The complete laser structure isgrown by metal organic vapour phase epitaxy technique and devices are fabricated throughstandard procedure using photolithography. Figure 1 shows the light versus current (L-I)characteristics of a laser diode operating at 853 nm in uncoated, unmounted conditions. Thepeak power in pulsed operation obtained is about 5.3 W. These laser diode structures weretested under pulsed operation at room temperature for 500 nanosecond pulse duration with aduty cycle of 1:1000. Lasing action was observed with a typical threshold current density ofabout 200A/cm2. Laser diode arrays consisting of 6-10 elements were also developed and testedfor operation in pulsed mode at room temperature. Figure 2 shows a laser array with 6 elementsunder operation very close to the current threshold at room temperature. These were installed inp-side down geometry where a metal single tip-electrode was used for back electrical connectionduring operation. Figure 3 shows the longitudinal spectrum of five laser diodes operating atdifferent wavelengths. There are a few more essential device processing steps like facet coating,

bonding and packaging of laser diodes which need tobe implemented before we could operate our deviceunder cw operation. Successful implementation ofthese steps will ensure an efficient heat removal fromthe chip and the usefulness of indigenous developeddevices. Progress of the laser diode development workat RRCAT will be summarized during this presentation.

Current (Amp)0 1 2 3 4 5

Pea

k P

ower

(W

att)

0

1

2

3

4

5

6

1:1000 duty cycle, 500ns

1:500 duty cycle, 1?sec

Fig.1 L-I characteristics of a laser diode Fig.2 A Laser diode array with 6 elements

NLS-6 14

Acknowledgments:

Authors would like to thanks Dr. V. C. Sahni, Prof. B. M. Arora and Prof. K. C. Rustagi for theencouragement and support and Shri U. K. Ghosh for the technical support.

References:

[1] P. Zory (Ed), Quantum Well Lasers, Academic Press, Boston, 1993.

[2] R. Diehl (Ed), High Power Diode Lasers, Springer, Berlin, 2000.

Wavelength(nm)700 750 800 850 900 950 1000

Inte

nsity

(co

unts

)

Fig. 3 Longitudinal spectra of five diode lasers operating at different wavelengths

NLS-6 15

High Reliability 980nm Pump Lasers for Erbium Doped FiberAmplifiers

B.R. SINGH, O.P. DAGA and KULDIP SINGHOpto-Electronic Devices Group,

Central Electronics Engineering Research Institute,Pilani - 333 031


High Power single mode 980nm lasers are the most important devices for the pumping of erbium-doped fiber amplifiers (EDFAs) used in the state-of-the-art dense wavelength division multiplexed(DWDM) systems operating in C-band. In recent years, the channel density in the fiber hasincreased remarkably resulting in requirements for enhanced pump power. This has put a strongfocus on the development of stable, reliable 980 nm laser diodes. Besides this, high power laserdiodes are also required for uncooled EDFA with less stringent gain requirement. For thisapplication also, the power output, stability and reliability are at a premium for compensatingthe adverse effects of high ambient temperature.

The present paper deals with the design, fabrication and performance of 980nm laser diodesdeveloped at CEERI, Pilani, India. The epitaxial structure InGaAs/AlGaAs/GaAs and the processparameters were optimized for stable high power monomode operation. The ridge wave-guidestructure provides current and optical confinement required for the single mode operation. Theridge wave-guide structure was processed using dry chemical etching with chlorine-basedchemistry. The electron beam evaporated Cr/Pt/Au and AuGe/Ti/Pt/Au was used for P and theN+ contact respectively. Facets were coated with Al

2O

3 and Al

2O

3/a-Si on the front rear facets

respectively using RF magnetron sputtering after cleaving. The layers and their thicknesseswere optimized for 5% (AR) and 90% (HR) reflectivity respectively. The diodes exhibited stablelinear kink free power ~ 180 mW at 300 mA drive current. The long-term reliability of thesedevices was evaluated by running the aging tests on a batch of eight diodes in a specially designedtest jig. The test set-up consisted of eight optically isolated segmented partitions, having mountingassembly for the laser diode, silicon photodiode and their biasing connections. The acceleratedreliability testing of the diodes were carried out at 65°C under constant power operating conditionof 75 mW. The extrapolated useful life at room temperature was observed to be more than10000 hours.

These CEERI developed laser diode chips were at first packaged at Heinrich Hertz Institute,Berlin, Germany and later at M/S Optiwave Photonics, Hyderabad. The laser diode chip andother components like thermoelectric cooler, varistor, thermistor, monitor photo-diode etc werepackaged in a 14-pin butterfly type industry compatible package and pin-out The packagedlaser diode module is a thermoelectrically cooled, pump laser source for 1550 nm erbium dopedfiber amplifiers. These modules are capable of delivering output power up to 90 mW (CW) at~50% coupling efficiency. The modules have also been successfully tested at C-DOT, Delhiand CGCRI, Kolkata for the pumping of EDFA in a booster amplifier configuration and exhibitedstable gain of ~15 dB for an input power of 0 dBm at 1550 nm.

NLS-6 16

Packaging of Semiconductor Lasers

K.S. KUMAR and T. MADHU KUMAROptiwave Photonics Ltd.,

#70, Rd #10, IDA Mallapur, Hyderabad-500076email : [email protected]

Semiconductor laser packaging is a complex process and is at an early stage of developmentwith limited automation. Only packaged devices allow for characterization under real operatingconditions and aging tests. In this talk, our efforts at package design and characterization ofsub-assembly packages during packaging process are reviewed. Electro-optical parameters suchas drive current, optical output power, wavelength and temperature stability are discussed. Inparticular, results from three different semiconductor lasers at 808nm, 980nm and 1550nmpackaged in TO-style, 14-pin butterfly and co-axial pigtail packages respectively are presented.

NLS-6 17

Design of Blue and Blue - Green Lasers

SUDAKSHINA KUNDUDepartment of Computer Science & Engineering,

West Bengal University of Technology,BF-142 Salt Lake Sector – I, Kolkata-700064

email : [email protected]

Multiple Quantum Well (MQW) structures are gaining much importance in the design of opticaldevices[1-2]. The materials that are commonly used in the design of optical devices are latticematched GaAs/AlGaAs, InGaAsP/InP, InGaAs/InP, InAs/AlSb pairs. Need for high-densityoptical memory is leading to the search for laser materials that can emit at shorter wavelengths.Semiconductors with band-gaps above 2.0eV are important materials for optoelectronic devices.In this context the wide band gap nitrides play a vital role in the design of optical devices in theblue and blue-green region[3]. Due to the Wurtzite structure, a polarization field is producedthat considerably changes the carrier distribution inside the well and affects the carrierconcentration [4-9]. In this talk the properties of Nitride based semi-conductor materials will bereviewed and the transfer matrix method will be adopted to calculate the energy levels of MQWstructures that can be extended to both periodic and non-periodic arrays. For the nitride quantumwells, a model for the computation of carrier distribution and carrier concentration will bepresented [10]. This model will include the change in the carrier concentration inside the wellsand the modification of the wave functions due to the polarisation field. In case of the multiplequantum well structures the transition energies will be computed. The calculation will be basedon a general theory that takes into account the energy dependent effective masses and ignoresthe effect of periodicity of the structure.

References :

[1] Agis A. Iliads and A.Christou , Invited paper:2003 Photonics West,Jan 29-Feb (2003)

[2] R.Schwedler, H.Mikkelsen, K.Wolter et al, J.Phys.111 France 4, 2341-2359 (1994)

[3] S.Nakamura and G.Fasol, ‘The Blue Laser Diode’ Springer-Verlag, Berlin (1997).

[4] F.Bernardini et. al., Phys. Rev.B.56 R 10024 (1997)

[5] F.Bernardini et. al., Phys Rev.Lett.79.3958 (1997)

[6] F.Bernardini et. al., Phys.Rev. B57 R9472 (1998)

[7] G.Marlin, A.Botchkarev, A.Rockett and H.Morkoc, Appl Phys. Lett 68 (1996)

[8] A.Bonfiglio, M.Lomascolo, G.Traetta, K.Cingolani, A.Di.Carlo, E.Della Sala, P.Lugli,A.Botchkarev and H.Morkoc, J Appl Phys 87 2289 (2000)

[9] S.H.Park and S.L.Chuang, Appl Phys. Lett 72 3103 (1998)

[10] B.Lahiri, R.Dutta and S.Kundu, Physica E 25449-445 (2005)

NLS-6 18

Excimer Lasers pumped by discharge and e-beam

VICTOR TARASENKOHigh Current Electronics Institute SB RAS,

2/3 Akademichesky Ave., Tomsk, 634055, Russiaemail : [email protected]

Results of the experimental study of powerful lasers pumped by a radially convergent electronbeam and a self-sustained discharge are presented. The laser system based on excimer laserswas created. Processes of exciplex molecules formation are described as well as the data on thehighest radiation parameters of the noble-gas-halides lasers are given.

The accelerators with radially converging e-beams pumping gas mixtures under pressure up to3 atm discharge were applied. The highest laser radiation energies up to 2 kJ have been obtainedat l = 308 nm with active volume of 600 l. Output of 100 J at l = 1.73 mm in Ar-Xe mixture and50 J at l = 2.03 mm in He-Ar-Xe mixture were obtained using the e-beam laser with activevolume of 600 l.

XeCl laser with active volume of 200 liters pumped by radially convergent e-beam is described.At pumping of the operating mixture Ar:Xe:HCl = 2 atm:40 Torr:2 Torr the radiation energy of650 J has been obtained. Duration of radiation pulse at FWHM was 350 ns.

Output energy of 110 J at l = 308 nm and 90 J at l ~ 250 nm were achieved in compact high-power e-beam laser with chamber 20 cm in diameter and 30 l in active volume. This e-beamgeometry was shown to be very promising for excitation of non-chain HF-laser media. HF-laserefficiency with respect to deposited energy as high as ~ 10 % and energy up to 200 J at l ~ 2.8mm were demonstrated.

Effect of pumping pulse parameters on the output of discharge XeF, XeCl, and KrF -lasers wasstudied using excitation by inductive and LC-generators. Experimental conditions providingmaximal performance of discharge lasers are determined.

The work reports development of discharge XeF, XeCl, and KrF lasers pumped by a generatorwith inductive energy storage. Two excitation modes with total and partial energy transfer intothe discharge circuit inductance were examined during experiments. In the first operation modeopening current was as high as 30 kA. The inductive generator produces current pulse up to 24kA in amplitude and 30 ns in duration. In the second excitation mode about 1/3 of the energystored in the storage capacitor was transferred into the circuit inductance which results in increaseof the current pulse up to 120 ns. The inductive generator produces voltage pulses across thelaser gap with very short rise-time and high amplitude providing excellent conditions for volumedischarge formation in all gas mixtures. Increase of the pumping pulse duration results in wideningof the radiation pulse up to 100 ns and significant improves the laser output parameters. Theoutput energy was up to 1.5 J.

This work was fulfilled under the ISTC partial financial support, Project # 2596.

NLS-6 19

Switch-less operation of TE Gas Lasers

D. J. BISWAS, J.P. NILAYA, M.B. SAI PRASAD, P. RAOTE and G. PATILLaser and Plasma Technology Division, BARC, Mumbai-400085


The function of a switch, which plays the most crucial role in the operation of the TE gas lasers,begins with the drawing of energy from the source and ends with the realisation of most of thisas the internal energy of the (lasing) gas. The operational life of a repetitive TE laser is primarilygoverned by the life of the switch that is expensive and of late there has been a well directedeffort towards its elimination, albeit partial, in the operation of such lasers. We have nowsucceeded in achieving the operation of a TEA CO

2 laser by totally dispensing with the service

of any extraneous switch. This has been possible by making the preionising spark channel, anintegral part of a UV preionised laser, to perform the dual role, that of a switch and also of a UVsource. Besides reviewing the topic, the talk would also aim at capturing the complexitiesinvolved in achieving switch-less operation.

NLS-6 20

Mechanism of Nonlinearity in Semiconductor Doped Glasses

K.S. BINDRAUltrafast Studies Section, Laser Physics and Application Division,Raja Ramanna Center for Advanced Technology, Indore-452013


The characterization of nonlinear optical properties of semiconductor nano-particles is importantfor fundamental understanding as well as from the device point of view. The linear opticalproperties of the semiconductor nano-particles are modified due to reduction in theirdimensionality. It is also important to know how does the nonlinear optical properties of nanoparticles compares with the corresponding bulk materials. In the transparency region(2hw>E

g>hw) of semiconductors two components contribute to the nonlinear response: the

intrinsic third order bound electronic nonlinearity and an effective fifth order nonlinearity dueto the free carriers generated by two-photon absorption (TPA). In general, the intrinsic nonlinearityis fast and the fifth order nonlinearity has a slow decay time, therefore, it is important to knowthe contribution of each of them separately.

The nonlinear optical properties of SDG’s have been studied experimentally using DFWMtechnique [1]. At low pump intensities the conjugate reflectivity varies like fourth power ofintensity signifying a fifth order nonlinearity due to free-carriers generated by TPA. Surprisinglyat higher intensities the conjugate signal showed a cubic dependence, which is typical of a thirdorder process. The cubic dependence does not necessarily indicate a third order process asusually assumed. Instead it is shown to arise due to reduction of effective intensity by nonlinearabsorption of the interacting beams.

Another widely used experimental technique for the measurement of nonlinearity is Z-scan.The Z-scan technique can be used to distinguish third and fifth order nonlinearity. For picosecondpulses using numerical simulations, we show that in case of dilute systems such as semiconductor-doped glasses, the Z-scan technique poses severe limitations [2]. Moreover, for a system likeSDG, the fifth order nonlinearity would appear as a third order nonlinearity. A clearerunderstanding can be obtained by a pump-probe Z-scan experiment [3]. The pump-probe Z-scan technique can unambiguously distinguish between the third and the fifth order nonlinearities.The results of pump-probe Z-scan experiment would be discussed. Closed aperture Z-scan profilesobtained with femtosecond and picosecond pulses are in complete contrast with each other [4].The significant modification in Z-scan profiles due to the contribution from various processesfor laser pulses with different temporal width would be discussed.

References :[1] K.S. Bindra, S.M. Oak and K.C. Rustagi, Phys. Rev. B 59 (1999) 2968.[2] K.S. Bindra, S.M. Oak and K.C. Rustagi, Opt. Commun. 168 (1999) 219.[3] K.S. Bindra, C.P. Singh and S.M. Oak, Submitted to Optics Commun.[4] K.S. Bindra and A.K. Kar, Appl. Phys. Lett. 79 (2001) 3761.

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Coherent Control of Molecular Dynamics with ShapedFemtosecond Laser Pulses

AJAY K. SINGH and SISIR K. SARKARRadiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai-400085


Femtosecod time resolution is essential for the investigation of ultrafast molecular and chemicalprocesses in real time. Study of ultrafast dynamics demand development of ‘state-of-the-art’spectrometers using sophisticated ultrafast laser systems. We at RPCD, BARC have been activelyinvolved in the setting up of two femtosecond transient spectrometers based on (i) collidingpulse modelocked dye laser (ii) CPA based multipass Ti: sapphire laser system. These twospectrometers have been used extensively for the investigation of molecular dynamics withtime resolution better than 100 fs. Our group has made a very useful contribution in the field ofultrafast chemical reaction dynamics in condensed phase.1,2 In recent years, the challenge hasshifted from the study of molecular dynamics to control over molecular processes. Femtosecondlaser sources are promising new tools for the research in the area of coherent control of moleculardynamics. Here, the broad spectrum inherent to femtosecond pulses is shaped in phase andamplitude to drive the molecule into the desired reactive state. A self-learning loop is employed,which uses a signal derived from the experiment as feedback. An evolutionary algorithm guidesthe search of the optimal field. The loop is repeated until an optimal pulse is obtained. Thefeedback-controlled pulse shaping has been successfully applied to control the moleculardynamics in complex systems. The closed-loop process is shown in figure 1. We have extendedour field of expertise in coherent control and the present work has been carried out in collaborationwith the group of Prof. Arnulf Materny at the International University Bremen, Germany.

Figure 1. Experimental Setup: The Stokes laser pulse of coherent anti-Stokes Ramanscattering (CARS) process (bottom, left) is shaped by a phase modulator setup (bottom,right). The spectrum resulting from this experiment serves as feedback for the evolutionaryalgorithm (top, right), which controls the pulse shaper during the optimization.

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Femtosecond pulses are spectrally broad and therefore, a selective excitation of specificvibrational modes of molecules is usually not achieved in ultrafast spectroscopy. In the presentwork, the feasibility of mode selective excitation is demonstrated in solution phase with broadbandfemtosecond laser pulses without electronic excitation in a coherent anti-Stokes Raman scattering(CARS) technique. A learning loop optimal control scheme is applied to a stimulated Ramanexcitation process. Modifications of the phase shape of Stokes pulses results in dramatic changesof the mode distribution reflected in coherent anti-Stokes Raman spectra. The ratio of signalintensities for different modes observed in the CARS spectrum served as feedback function foran evolutionary algorithm and is responsible for the optimization for the selective relativeenhancement or suppression of one or more vibrational modes in the ground state (Fig. 2) overthe complete coherence lifetime.2-4 The temporal resolution after optimization is still high enoughto investigate the mode specific ultrafast dynamics. Also the targeted suppression of Ramanlines in the CARS spectrum would have considerable advantages for frequency-resolvedspectroscopy. The spectral filtering is also shown to be molecule specific, which is of interestfor filtering out spectral contributions of specific molecules in a mixture. The selective excitationof specific molecular modes is an important stepping stone towards the realization of the controlof chemical reactions. Mechanism responsible for such mode control and its emerging applicationsin various branches of science will be discussed.

References :

[1] A.K. Singh, A.C. Bhasikuttan, D.K. Palit, and J.P. Mittal, J. Phys. Chem. A, 104, 7002(2000)

[2] A.K.Singh,J.A. Mondal,G.Ramakrishna, H.N.Ghosh,T.Bandyopadhyay and D.K.Palit,J.Phys.Chem.B, 109, 4014 (2005)

[3] J. Konradi, A.K. Singh, and A. Materny, Phys. Chem. Chem. Phys., 20, 3574 (2005).

[4] J. Konradi, A.K. Singh, and A. Materny, J. Photochem. Photobio.A. Chem., 180, 289(2006)

Figure 2.: Mode Selective Excitation: fs CARS spectra taken with transform limited pulses (A,D)and phase shaped (B,C,E and F) Stokes pulses from Toluene (left side) and mixture of benzene andchloroform (right side) with FROG traces of the corresponding Stokes pulses

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Coherent XUV radiation from laser plasma plumes through high orderharmonic generation

PRASAD A. NAIK, H. SINGHAL, V. ARORA, U. CHAKRAVARTY, J.A. CHAKERA,R.A. KHAN, M. RAGHURAMAIAH, S.R. KUMBHARE and P.D. GUPTA

Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore 452 013

R. GANEEVAkadempribor Scientific Association, Tashkant-700125, Uzbekistan


A bright, monochromatic, coherent source in the extreme ultraviolet (XUV) spectral region hasmany applications. X-ray lasers and high-order harmonics are two coherent sources of radiationin this region. Although the latter has a better coherence than the x-ray lasers, they are notmonochromatic. They can be used as a monochromatic, coherent source if one selects someparticular harmonic using a monochromator, albeit with a loss of intensity. The use of appropriatephase matching conditions to replace the well-known plateau of the harmonic distribution by anintense single harmonic is a step in this direction to give the harmonics an edge over the x-raylasers. In particular, the resonance between one of the harmonic wavelengths and some excitedstates of the neutrals or singly charged ions can lead to a considerable enhancement of theharmonic yield for some specific harmonic orders. The use of weakly excited plasma plumes,instead of gas jets, can exploit the availability of a much wider range of target materials, and thisincreases the possibility of the resonance of an ionic / atomic transition with a harmonic order.Further, tuning of high order harmonics may be used to match the wavelength of a particularharmonic order with the lasing wavelength so that the harmonic radiation acts as a coherentseed for lasing, leading to a higher coherence in the x-ray laser.

We have experimentally studied high order harmonic generation using an ultrashort, ultrahighintensity Ti:sapphire laser (100 mJ, 50 fs, 10 Hz), using plasma plume as the target. The harmonicyield was optimized by adjusting the position of the ps laser focusing lens as well as the fs laserfocusing lens, delay between the ps and fs laser pulses, and the distance of interaction of the fslaser beam from the target surface. Laser pulse chirping, by adjusting the separation of thecompressor gratings, has been used for changing the frequency of the high order harmonics.Various peculiarities have been observed in different materials like In, InP, InSb, GaAs, GaP,Ag, Cr etc. High order harmonics up to 61st order (13nm ) have been observed for silver plumes.An enhancement by a factor of 200 has been observed for 13th harmonic in indium plasma.Further, enhancement of some harmonics has been seen in GaAs plasma plumes, whereasvanishing of some particular harmonic has been observed in chromium plasma. Tuning of theharmonics by up to 0.8 nm has been obtained by controlling the chirp in the fundamental. It isdemonstrated that the enhancement / extinction of harmonic intensities can be accomplished bytuning the wavelength of the harmonics. The effect of wavelength tuning on these peculiaritiesindicates the role of atomic / ionic line resonance with the harmonics.

The details of the experimental investigations and the results will be presented along with ourpresent understanding of the various processes involved in the high harmonic generation.

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Structure, Dynamics and Rheology of Soft Materials usingLaser Light Scattering Techniques

SURESH BHATComplex Fluids & Polymer Engineering Group,

Polymer Science & Engineering Division, National Chemical Laboratory,Dr. Homi Bhabha Road, Pune – 411008


Soft Materials or Complex Fluids comprise materials which are neither simple liquids norcrystalline solids but have an intermediate behaviour depending on the length and time scales ofobservation. These include colloids, polymers, surfactants, emulsions, liquid crystals and variousbiomaterials including DNA and proteins. Due to the increasing use of soft materials in today’sindustrial applications, the soft matter area has seen tremendous research activities recently.Soft materials find use in food, paint, cosmetics, pharmaceutical, chemical industry etc. and lifewithout them is unimaginable. These materials typically possess structures which are muchlarger than atomic or molecular scales; the structure and dynamics at the mesoscopic scalesdetermine their macroscopic physical properties. Soft matter systems are often seen in the formof non-equilibrium states like gels, glasses etc which have very slow dynamics makingexperimental realizations difficult. Moreover understanding the interactions between variousconstituents of a soft matter system is important to improve the structure and stability of aproduct. Laser light scattering is a versatile technique to study the structure and dynamics ofsoft materials as the length scales of interest in these systems match well with the wavelength oflasers used in these instruments. However, information obtained using conventional lightscattering techniques are mostly incorrect due to the overwhelming contribution of multiplelight scattering from turbid suspensions; a situation commonly encountered in industrial samples.Recent developments in light scattering instrumentation have tremendously improved thecapability of light scattering instruments in performing experiments at very high concentrations.In this talk, I will be discussing about recent advances in light scattering instrumentation like3D-dynamic light scattering (3D-DLS), Ultra-small angle light scattering (USALS) and DiffusingWave Spectroscopy (DWS) and show how meaningful information about the structure, dynamicsand rheology of soft matter systems can be obtained using such instruments. As an example,results will be presented on yoghurt formation from milk covering the whole sol-gel transition.

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Optical Coherence Tomography

K. DIVAKAR RAO, Y. VERMA and P.K. GUPTALaser Biomedical Applications & Instrumentation Division,

Raja Ramanna Centre for Advanced Technology,Indore - 452 013


Optical coherence tomography (OCT) has emerged as a new imaging modality, which can providecross sectional images of tissue structure on the micron scale resolution in vivo and in real time.OCT relies on the principle of low coherence interferometry, wherein light from a broadbandsource backscattered from a sample is mixed with the reference light using Michelsoninterferometer geometry. The conventional OCT systems using superluminescent diodes withnarrow bandwidth at the near infrared region can acquire tissue images with a resolution of 10-20 mm in 3D with >100 dB sensitivity, whereas ultrahigh resolution down to 1mm has beendemonstrated using super continuum light sources. The depth of penetration of OCT for highlyscattering tissues (unlike eye) is limited to 2-3 mm due to attenuation and scattering inside thetissue. Developments in Fourier domain OCT methods showed an enhancement of 10-20 dB inthe signal to noise ratio without any need for reference arm scanning. OCT has already becomea regular clinical diagnostic tool for retinal imaging in several hospitals and new systems areemerging for imaging arteries, Gastrointestinal track and skin. Functional extensions such asblood flow imaging, spectroscopic imaging, are being demonstrated. In addition to the clinicalapplications, there has been intense current research to introduce molecular specific imaging inOCT with varying degree of success. In this talk, a brief overview of OCT will be presentedwith particular emphasis on the work being done at RRCAT.

References :

[1] A F Fercher, W Drexler, C K Hitzenberger and T Lasser, Rep. Prog. Phys. 66, 239–303(2003).

[2] A. Gh Podoleanu, The British journal of Radiology, 78, 976 (2005)[3] K. Divakar Rao, Y. Verma, H.S.Patel and P.K.Gupta, Current science 90, 1506 (2006).[4] K Divakar Rao, M Choma, S Yazdanfar, A M Rollins, and J A Izatt, Opt. Lett. 28, 340

(2003)

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Applications of Raman Spectroscopy in Cancer Management

C. MURALI KRISHNACenter for Laser Spectroscopy, Manipal Academy of Higher Education,

Manipal - 576104email : [email protected], [email protected]

Cancer is one of the serious health problems in developed as well developing countries. Canceris a complex family of diseases and carcinogenesis is a multi-step process. A large number ofbiochemical steps are involved in the progression of a tumor from a homogeneous proliferatingclone to a group of heterogeneous subpopulation of cells. Conventional approach of diagnosis/screening of cancer is based on morphological changes which are often rather late signs of anadvanced disease. Prognosis is shown to heavily depend on stage of diagnosis, earlier thediagnosis better the outcome. Hence, there exists a need to develop new methods that are sensitiveto molecular level variations, rapid and more objective for early diagnosis, screening, monitoringof therapy and early detection of recurrence, if any. Optical spectroscopy, coupled withmultivariate tools, is uniquely poised to provide potential alternatives to conventional diagnosis.Several studies have demonstrated the importance of Raman spectroscopy as a clinical tool incancer and other clinical conditions1.

In the present paper we discuss results of our recent Raman and Raman microspectroscopystudies pertaining to cancer management. We have developed tissue Raman spectroscopy modelsto discriminate normal and abnormal conditions in oral, cervix and breast cancers2. Blind studiesare being pursued to evaluate these models. We have also carried out pilot Raman studies onovarian, stomach and colon cancers3. Less invasive biopsies like Pap smear, brush biopsies arethe ideal specimens for optical microspectroscopy methods at the cellular level for early diagnosisor identification of resistance phenotype. Real life specimens are very inhomogeneous in nature.Hence, efficiency of Raman microspectroscopy in discriminating a cell type in randomlydistributed mixed HL60+MCF7 and MCF7+MES-SA cell populations is evaluated3. Multidrugresistance is a serious handicap in chemotherapy of cancers. In our exploratory studies, wecould delineate wild and MDR phenotypes of leukaemia cell HL60 (HL60, HL60/DOX, HL60/DNR), breast cancer cell lines (MCF7 and MCF7/vp) and uterine cell line (MES-SA and Garf)4,5.Fresh tissues in saline are ideal samples for optical pathology. However, evaluation of suitabilityof ex vivo handled tissues is necessitated due to severe constraints in sample procurement,handling and other associated problems with fresh tissues. Among the ex vivo handled tissues,formalin fixed tissues are found to be better for discrimination as well as in content of biochemicalinformation6. And we have further evaluated formalin fixed tissues in conditions where variationsin biochemical composition expected to be relatively small which could be a limitation offormalin-fixed samples in optical pathology6.

I am grateful to Dr. V.B. Kartha, Dr. G. Ullas, CLS, MAHE; and Pr. M. Manfait and Pr. G.D.Sockalingum MeDIAN, Univ. of Reims, France. All the clinical collaborators from KMC, MAHE,Manipal and CHUV, Reims, France are gratefully acknowledged. Financial support from

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BOYSCAST Scheme, DST, ICMR, DAE-BRNS, Liegue Haute, and Univ. of Reims isacknowledged.

References :

[1] Hanlon EB et. al., 2000 Phys. Med Biol 45: R1-R59

[2] Malini R et. al., Biopolymers , 81,179-193, 2006; C. Murali Krishna, et. al., RamanVibrational Spectroscopy, 41, 136-141, 2006; M.V.P. Chowdary et. al., Biopolymers, InPress 2006.

[3] K. Kalyan Kumar et. al., Vibrational Spectroscopy communicated; Keerti et. al., SpectraChemica Acta. communicated

[4] C. Murali Krishna et. al., Vibrational Spectroscopy, 38, 95-100, 2005.

[5] C. Murali Krishna et. al., Biopolymers, , 82, 462-70 2006; C. Murali Krishna et. al., Biochim.Biophys. Acta 1726, 160-167, 2005

[6] C. Murali Krishna et. al., Applied Spectroscopy, 58, 1128-1135 (2004); C. Murali Krishnaet. al., Biopolymers. 79, 269-76, 2005; C. Murali Krishna et. al., Analytical and BioanalyticalChemistry, In Press 2006

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Measuring plasma opacity using X-ray Lasers

G. J. TALLENTSDepartment of Physics, University of York,

York YO10 5DD, United Kingdomemail : [email protected]

The opacity of hot dense plasma is critical in the modelling of radiation diffusion in the Sun andother stars, in understanding the interaction of free-electron lasers with material and in theprediction of the properties of materials under extreme conditions. Extreme ultra-violet (EUV)lasers have been produced in two ways - using ‘wiggler’ technology to produce free-electronlasers and using a laser-plasma based pumping mechanism. In this talk, I will introduce laser-plasma EUV lasers and present a new measurement of the opacity of hot dense plasma usingthese EUV lasers. It is shown for iron plasmas of 30 - 300 eV and density 0.3 - 0.001 gcm-3 thatthe bound-bound transitions of a large number of spectral lines (> 3000) dominate the opacity.The use of EUV lasers to measure the rate of ablation of solid material during laser irradiationwill also be discussed. Ablation is one of the key parameters in direct drive laser-fusion andother applications of laser-produced plasmas.

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Copper Vapour Lasers - A review and development at RRCAT

J.K. MITTALLaser Systems Engineering Division, RRCAT, Indore 452013


The Copper Vapour Laser (CVL) is the most powerful and efficient laser in the visible part ofspectrum. Its use as a pump beam for tunable dye laser for application in laser isotope separationhas accelerated the technological growth of the laser. The high peak power as well as highaverage power of CVL has varied applications in material processing. Over a period of morethan 40 years ever since the first demonstration of CVL by Walter et al in 1965, the CVL hasdeveloped into a mature technology and efforts are being made to increase the laser power froma single laser head, efficiency > 1% and operation in sealed-off condition.

There are four type of CVL i.e. Copper Vapour Laser (CVL); Copper Bromide Vapour Laser(CBL); Copper Hybrid Laser (CuHyBrID) and Kinetically Enhanced Copper Vapour Laser(KE-CVL). In all the four type of CVL, active medium is copper and the difference is in themethod of introducing active species i.e. copper into the discharge. Each type has its own merit.All the three types of CVL except copper bromide laser are flowing gas type. The CuHyBrIDand CBL are low tube temperature (500-6000 C) operating laser and remaining two are hightube temperature (1500-16000 C) operating laser.

The electrical power is normally switched into the active medium by using hydrogen thyratron.The thyratron is costly and has limited operating life of 1000-1200 hours. In addition, thyratronis not easily available because of export restriction to India. With the development of fast switchingsolid state switches, it has become possible now to replace hydrogen thyratron by solid stateswitches. Solid state switches are more reliable and cost effective.

Over a period of last 20 years, Laser Systems Engineering Division (LSED) at Raja RamannaCentre for Advanced Technology (RRCAT) has developed copper vapour laser giving averagelaser power > 50 W from a single laser and delivered many laser systems of 30 W & 40 W laserpower. The prototype copper HyBrID laser giving 40 W laser power at an electrical to opticalconversion efficiency of 1.5% has already been demonstrated and now planning to increase thelaser power up-to 100 W from the single laser. A table top KE-CVL giving more than 90 Wlaser power from the single head has been demonstrated. Recently, we have taken up thedevelopment of CBL and demonstrated its operation in sealed off condition. Recently, laserdeveloped at RRCAT are being designed using SMPS and solid state switches.

In this talk, a review of technological development of CVL and our efforts at RRCAT indevelopment of CVL will be presented.

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Generation and Characterization of Ultrashort Laser Pulse

P.K. DATTA, S. MUKHOPADHYAY and S.K. DASDepartment of Physics & Meteorology, IIT Kharagpur - 721302


Over the last three decades there has been remarkable progress in the area of ultrashort opticalpulse generation directly from a laser oscillator and till date an intensive research is going ontowards all solid-state ultra-fast laser technology. Several mode-locking techniques have beenemployed to generate ultrashort pulse train and increased the peak power. Some unique featuresof the ultra-short pulse find their wide applications in basic research, medical science and in theindustry. The high peak power of ultra-short laser pulse is used in nonlinear optical frequencyconversion and optical parametric oscillator, material processing and material micro-structuring.High peak power of ultra-short laser pulse is being utilized in medical science for precisioncutting and surgery and also in nonlinear microscopy. With the journey of generating shorterand shorter pulses, there was a parallel effort on theoretical understanding of the pulse formationmechanism through mode-locking a laser. Siegman-Kuizenga’s analytic theory on active mode-locking laid the foundation stone in this effort1. The theory on fast saturable absorber mode-locking by H. A. Haus2 in 1975 was the pioneer for studying mode-locking stability. He couldget a closed form solution for mode-locked pulse in case of fast saturable absorber only. Arevolution came with the demonstration of ultra-short pulse generation by Kerr-lens mode-locking (KLM) in 1991. This technique relies on the Kerr nonlinearity and manifests the effectof a fast saturable absorber. Several groups there after continued to work on KLM and sub 100fspulse is being regularly generated using gain medium like Ti: Al

2O

3, Cr: Frosterite, Cr: LiSAF

etc. Although the KLM has also been demonstrated in Nd:YAG for sub 10ps pulse generation,because of the requirement of high peak intensity to realize KLM, the technique is efficient in fsregime. For successful KLM it needs precise cavity design. Recently semiconductor saturableabsorber mirror (SESAM) has become very efficient for mode-locking of solid state lasers.These devices are typically grown by molecular beam epitaxy. SESAM contains one or morequantum well, grown on a mirror structure and provides an intensity dependent absorptioncoefficient. In the first stage, high fineness anti-resonant Fabry-Perot saturable absorber (A-FPSA). was tried for increased damage threshold. Later on several device structure like ARcoated SESAM, low fineness A-FPSA, and dispersion compensating SESAM were introducedto control the loss modulation and saturation dynamics optimally for satisfactory mode-locking.The dynamical parameter of the saturable absorber can be tailored desirably by sophisticatedand controlled growth mechanism of the saturable absorber. As such the technology for fabricatingan SESAM is sophisticated and costly. Mode-locking of laser using second order nonlinearoptical interactions has become simpler techniques as compared to the other processes mentionedabove. One scheme, known as nonlinear mirror (NLM), uses a frequency doubling nonlinearcrystal (NLC) and a dichroic output coupler to provide direct amplitude modulation of intracavity

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radiation. Another technique called cascaded second order mode-locking (CSM) uses a suitablyplaced intracavity aperture in addition to a frequency doubling NLC and a dichroic outputcoupler. However, the nonlinear mirror is the simplest technique for mode-locking solid statelasers and has enough commercial potential. It requires neither any sophisticated technology torealize nor it requires interferrometric cavity length control. The merit of a mode-locked laserdepends on the stability of the mode-locking. The stability of mode-locking depends on thedynamical behaviour of the laser loss saturation. The present talk explores the saturable absorberparameter of a NLM3-4, study of stability regime of NLM and compare it with other mode-locking techniques. Innovative technique is employed and studied for inverse saturation of laserloss to get stable, self-starting, self-sustained and power scalable cw mode-locking.Characterization of ultrashort pulses is also discussed.

References :

[1] D. I. Kuizenga and A. E. Siegman, IEEE J. Quantum Electron., QE-6, 803 (1970)

[2] H. A. Haus, J. Appl. Phys., 46, 3049 (1975)

[3] P K Datta et. al., Optics Express, 12, 4041 (2004)

[4] P.K. Datta et. al., Appl. Phys. Lett., 86,151105 (2005)

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Confocal Laser Scanning Microscopy in Environmental Biotechnology,Biofilms and Microbial Corrosion Research

T.S. RAOWater & Steam Chemistry Division,

Bhabha Atomic Research Centre Facilities,Kalpakkam, Tamil Nadu – 603 102


Environmental biotechnology can signify many things; exploitation of gene pool as a resourcefor the search and discovery of novel compounds, gene transfer, pollutant degrading and alsoits application in biotechnological processes for environmental benefits. Ominously, biofoulingand biofilm formation are of great concern to many industries, viz., marine, food, water, miningand medicine. The economic consequence of biofilms / biofouling is thus significant, becausebiofouling increases water resistance, fuel consumption and promotes corrosion of metal surfaces.Industrially, biofilms pose problems in cooling circuits, wherein they reduce heat transferefficiency resulting in significant pressure drop in the condensers as well as impairing theperformance of associated ancillary systems. Predicting the type, rate and extent of biofilmformation is beneficial in environmental studies, in designing of industrial cooling systems andin operation of industrial equipment which is prone to biofouling. On the other hand, biofilmsalso contribute substantially to nutrient cycling in aquatic ecosystems. Microbial biofilms havebeen hypothesised as a stimulus for the settlement and metamorphosis of marine invertebrates.Microbial corrosion processes at metal surfaces are associated with microorganisms. Thecontribution of microorganisms to corrosion has been assessed using a variety of optical andelectron microscopy techniques.

Many molecular biology tools coupled with confocal laser microscopy have now become routinefor analysis of microbial biofilms and are providing valuable insights into structure and functionalrelationship in microbes. Confocal Laser Scanning Microscopy (CLSM) allow the examinationof hydrated biofilms and yield clean, three-dimensional images of living biofilms in real time.CLSM has also shown that 75 to 95% of the volume of bacterial biofilms is occupied by thematrix and water; cells are concentrated in only 5-25% of the lower or upper layers. Recently,CLSM has been employed to study corrosion phenomena. The technique provides informationabout the morphology of microbial cells and colonies, their distribution on the metal surface.The technique can also reveal the type of corrosion attack (e.g. pitting or uniform corrosion,localised attack, crevice corrosion etc.) and also provides a 3D view of the corrosion pit ordanmage. To confirm microbial corrosion, specific activities of the microbes at the site of materialdeterioration / corrosion should be demonstrated, molecular tools and CLSM technique canprovide such valuable evidence.

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Multicolored Atomic Coherence

HARSHAWARDHAN WANAREDept. of Physics, IIT Kanpur-208 016


Atomic coherence has revolutionized the area of quantum optics, with dramatic effects likerendering an atomic gas medium transparent, laser action without population inversion, super-slow and superluminal pulse propagation and many more such effects. At the heart of thesephenomenon lies the creation of coherence between various atomic states. Such coherence isgenerated by ingenious coupling of different atomic levels by a few extremely stablemonochromatic light fields. The Coherent Population Trapping (CPT) state is one such statewhich results from an interplay of light and atom dynamics resulting in maximum atomiccoherence and significantly reduced spontaneous emission. It forms the basis of most of theamazing effects mentioned above and much more. Until now all these atomic coherence effectshave relied heavily on the monochromatic nature of light. These coherent effects degradesignificantly as the frequency content of the light fields is increased because it destroys thedefinite phase relationship between atomic states. We have recently demonstrated the possibilityof multicolored CPT [1], where we obtain large atomic coherence at a series of frequencies forexcitation with a specifically structured field. We propose excitation of the atom by frequencymodulated fields. Furthermore,a judicious choice of modulation characteristics allows coherentcontrol,wherein one can selectively switch on or off the occurrence of CPT at specific frequencies.The response of the atomic system to such fields is calculated nonperturbatively. A new techniqueis developed to compute two-dimensional tridiagonal matrix equations. This generalizedtechnique provides the vital methodology needed to calculate the response of such systems inthe strong modulation regime and for arbitrary field strengths.

Reference :

[1] Harshawardhan Wanare, Phys. Rev. Lett., Vol. 96, 183601 (2006).

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Optical pumping and coherence effects in flourescencefrom a four level system

ANDAL NARAYANANOptics Lab, Raman Research Institute, Sadashivnagar,

Bangalore - 560 080email : [email protected]

An effective four-level system around the D2 line of 85Rb at room temperature, is experimentallyinvestigated by fluorescent studies under the action of two driving fields L1 and L2. This systemexhibits unique features in fluorescence as a function of frequency seperation between L1 andL2. In particular, at two-photon resonance, when the Rabi frequency of L1 exceeds that of L2,signatures of Electromagnetically Induced Transperancy effect (EIT) arising from the three-level sub-system is present as a sub-natural dip in fluorescence from the fourth level. Atcomparable strengths of L1 and L2 the fluorescence features indicate a regime, where the effectsarising from optical pumping and EIT effect due to ground hyperfine level coherence coexist.We see in the coexistence regime, saturation effects arising from difference frequency crossing(DFC) resonances and optical pumping around the EIT window. At low strengths of L1, allsigns of coherence vanishes from the system and the fluorescent features result from incoherentoptical pumping through the Autler-Townes split states of the excited state hyperfine levels,which are split due to the stronger L2 laser. The dominant role of the L1 laser in creating arobust transparency signal even in the presence of an off-resonant excitation is brought out. Theresults are supported by density matrix calculations.

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Synthesis and Surface Modification of Ceramic Coatings using Lasers

R. KRISHNANMaterials Science Division,

Indira Gandhi Centre for Atomic Research,Kalpakkam - 603102


Ceramics, traditionally known for their high temperature strength, hardness and chemicalinertness, also possess rich electrical and magnetic properties. Scientific challenges to combinethese properties with the desirable properties of metals have led to the development of ceramiccoatings over metallic substrates. Pulsed Laser Deposition (PLD) has proved to be a suitabletechnique for the deposition of stoichiometric and crystalline ceramic thin films with acombination of physical properties. Lasers are also used to modify and improve surface propertiesof a component for a variety of applications. This article covers the use of ns pulsed Nd:YAGlaser for the synthesis of metal nitride thin films through reactive processing from respectivemetallic targets. Use of high power CO

2 laser to modify the ceramic coatings prepared by other

techniques to enhance the surface properties will be presented. The use of milliwatt lasers tocharacterize the modified surfaces for structure, roughness and density will also be discussed.

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Laser based Instruments for flow visualization,speed and distance measurement

ASEEM SINGH RAWATLaser & Plasma Technology Division,

Bhabha Atomic Research Centre, Mumbai-400085email: [email protected]

Laser is an excellent tool for measurement application. It offers the advantage of non-contact,non-destructive and fast measurement. Laser based Instruments have Industrial as well as scientificapplications. Some of the applications of Laser in Instrumentation on which we have worked are:

(1) Flow visualization using Particle Image Velocimetry (PIV) technique(2) Projectile speed measurement based on time of flight principle(3) Distance/displacement measurement using Optical triangulation principle

In PIV, a light sheet, generated by high power pulse laser, illuminates a plane along the directionof flow and image of microscopic tracer particles that follow the fluid or gaseous flow are recordedby CCD camera. Two such consecutive images (corresponding to two laser pulses) are recordedwithin short interval of time and then image processing methods are employed to determine particlesdisplacement and hence the flow velocity at different points. Most important contribution of PIVis that it gives near- instantaneous whole field velocity. PIV not only has all the advantages of aflow visualization method, but it can also provide valuable quantitative information. Anexperimental PIV set-up and its results are presented in the talk.

Diode laser has found wide application in Laser based instrumentation due to its specialcharacteristics of compact size, low power requirement and low cost. In Laser based projectilevelocity measurement, a horizontally moving projectile interrupts two Diode laser generated lightsheets (vertical and parallel to each other) separated by a fixed known distance and the timebetween two interruptions is measured electronically to calculate the speed. A portable, standaloneinstrument based on this technique is discussed which can measure velocities up to 4000 m/s withaccuracy better than 5 %. It is also possible to measure Rebound velocity of a spherical object ofknown diameter using single light sheet. Here the time taken by the object to cross the light sheetis measured accurately to calculate the velocity. It is more suitable for low velocities. A compactstandalone instrument for Rebound velocity measurement using Diode laser, which can measurethe falling as well as rebound velocity of an object and calculate ratio of the two velocities is alsodiscussed.

Optical triangulation technique is most suitable for measurement of short distances up to 10 meters.In this method a triangle is formed between light source (laser), target and the lens-detector assembly.When laser beam falls perpendicular on the target, it scatters light in many directions (diffusereflectance), some of the scattered light is collected by the receiving lens and focused on thedetector. Any movement of the target results in displacement of the focused spot on the detector.By measuring the displacement of the spot on detector, target displacement and also its distance iscalculated. Measurement times of less than 10 ms are common, allowing real-time study of movingor vibrating objects. A Diode laser based standalone instrument for distance measurement in therange of 1 meter to 2 meter using Optical triangulation technique is explained in the talk.

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Applications of High Power Solid-State Lasers in Nuclear Field

B. N. UPADHYAYASolid State Laser Division, Raja Ramanna Centre for Advanced Technology,

Indore - 452013email : [email protected]

Since the advent of solid-state lasers, it has evolved into three generations: lamp-pumped solid-state lasers, diode-pumped solid-state lasers and diode-pumped fiber lasers, which differ fromeach other mainly in material and pumping geometry. Solid-state lasers with fiber optic beamdelivery have been found to be extremely useful tool for material processing applications suchas cutting, welding and drilling in radioactive environment due to ease in tool handling, flexibility,non-contact nature, longer tool life, low MANREM consumption with enormous time and costsavings. Although, lamp pumped solid-state lasers have about 3-4% efficiency, over the last twodecades, they have been proved to be the most rugged and widely used system in harshenvironmental conditions. In order to enhance quality and range of material processingapplications, higher and higher power Nd:YAG lasers with improved beam quality and beamdelivery through optical fibers having smaller and smaller core diameter are being developedworld-wide.

Solid State Laser Division has an ongoing programme for the development of kW level CW andpulsed Nd:YAG lasers, for both lamp and diode pumped versions. During the last few years, wehave commissioned about fifteen numbers of lamp pumped pulsed Nd:YAG lasers having multi-port time-shared fiber optic beam delivery with about 5kW peak power for various specific turnkey projects in nuclear environment at BARC, IGCAR, BRIT, NFC and NPCIL. This remotelyoperable laser system has been engineered for its robustness with proper fixtures and toolingsfor various material processing operations on industrial scale related to nuclear field and innuclear reactor in particular. In a major breakthrough, this laser system has been successfullyexploited for en-masse coolant channel replacement (EMCCR) in a pressurized heavy waterreactor (PHWR) at Narora Atomic Power Station. This talk will brief about the developmentscarried out for various applications performed in nuclear field.

It has been recognized that solid-state lasers can potentially address several applications ofthick stainless steel cutting and deep penetration welding along with decommissioning anddecontamination in nuclear environments, however this can be addressed only with multi-kilowattlevel lasers. Recently, high power fiber laser technology has grown in robustness and reliabilitywith easy power scaling and less thermal problems as compared to their conventional lamp/diode pumped counterparts. Fiber lasers use double-clad fiber architecture and can producesingle-mode laser output without requiring single mode diode pump sources. There has been agrowing interest in high power Yb-doped fiber lasers as a potential replacement for bulk solidstate lasers in many applications due to their inherent advantages in terms of higher efficiency,single-mode output, long life of maintenance free operation (~100,000hrs.), no coolingrequirement and no risk of misalignment by means of intra-core Bragg grating mirrors. Further,wide absorption band of Yb-doped fibers and long tuning range makes it a unique solid-state

NLS-6 38

laser source for various applications. To date, there are reports about the development of up to2kW single mode output from an Ytterbium fiber laser at 1075nm with record brightness, ultralong life, maintenance free operation and a compact footprint, which can be considered as themost intense CW laser of any kind. With such intense lasers, it is possible to undertake most ofthe material processing applications. IPG Photonics, USA has also commercialized a compact20kW multimode CW fiber laser with 25% wall plug efficiency, which can potentially addressmaterial processing applications such as “infield” rock and concrete drilling/cutting, which arenot possible with any other kind laser system and seams to of tremendous use in nuclearcommissioning and decommissioning projects. We are also engaged in the development of highpower fiber lasers with initial success in developing more than 10Watts of single mode CWfiber laser with an optical-to-optical conversion efficiency of about 73%. Further, it is plannedto achieve ~100 Watt single mode CW fiber laser, which will also provide a road map fordevelopment of kW level CW fiber lasers for nuclear applications.

This talk will also cover a state-of-the-art scenario of all the three generations of high powersolid-state lasers and our efforts in this direction. We will further discuss about our ongoingefforts in nuclear applications and future directions.

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Spectra of doped laser material and upconversion lasers

S. B. RAILaser and Spectroscopy Laboratory,

Department of Physics, B. H. U., Varanasi-221 005email : [email protected]

Optical properties of large number of rare earths (Dy, Pr, Ho, Er, Eu, Tm, Nd, Sm etc.) dopedglasses (borate, silicate, fluoroborate, oxyfluoroborate, phosphate, tellurite etc.) have been studiedextensively using absorption, fluorescence, photo-acoustic and excitation techniques and variousoptical properties such as oscillator strength, stimulated emission cross section, branching ratio,radiative lifetime etc. have been determined. The lifetime of various levels of these rare-earthshave been measured using fluorescence decay technique. These parameters have been used tojudge the suitability of a particular transition for lasing. The effect of temperature on the emissivecharacteristic of the glass have studied in detail. We have also studied the effect of irradiation byneutron and ¡ -ray on the fluorescence spectrum of the glass. It is observed that on irradiationthe triply ionized rare earth change its state of ionization. This results a drastic reduction influorescence intensity. It also disrupts the lattice. The rare earth however regains its earlierionization state however the lattice is permanently disrupted.

The rare earth doped glasses have also been found to convert the NIR/Visible radiation intoVisible/UV radiations. Thus the Er3+ ion and Ho3+ doped tellurite glasses on pumping with NIRshow very intense green upconversion. They also show upconversion emission in red, blue andin UV region. Tm3+ + Yb3+ doped in tellurite glass show very intense blue and red emission.Dy3+ doped in phosphate glass show intense upconversion in yellow and orange region.

Rare earth doped glasses have also been found useful in monitoring the temperature of thesource used for heating the sample. If one monitors the fluorescence emitted from the twoclosed lying levels of the rare earth, the ratio of the intensity emitted by the two levels can giveus the temperature of the source. This can also be achieved by measuring the lifetime of the twolevels at different temperatures. We use this technique to measure the temperature of the sourceby using fluorescence emitted by 4S

3/2 and 2H

11/2 levels of Er3+ and 5F

4 and 5S

2 levels in Ho3+. We

also measured the temperature using thermocouple and a good agreement is marked in betweenthe values measured in the two ways.

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Growth of large, device quality NLO crystals by flux growth method

S. GANESAMOORTHY, INDRANIL BHAUMIK,R. BHATT, A. K. KARNAL and P. K. GUPTALaser Materials Development and Devices Division,

Raja Ramanna Centre for Advanced Technology, Indore-452 013email : [email protected]

At LMDDD considerable efforts have been put on the indigenous development of crystal growthworkstations for the growth of large size, device quality, nonlinear optical (NLO) crystals, bythe flux method. This objective required development and integration of a number of sub-systems.These include multi zone resistive heated furnaces capable of operation up to 1200 °C and withoptions to alter the gradients from near zero gradient to 10-15 °C/cm to meet the requirement ofthe crystal being grown, precise crystal pulling assembly (0.01 mm/h to 18 mm/h) to achieve therequired growth rate and an arrangement for accelerated bi-directional rotation of the seed tobring fresh nutrients near to the growing crystal more efficiently. Crystal growth workstationswere assembled by incorporating these sub-systems and have been successfully utilized for thegrowth of prominent NLO crystals such as KTiOPO

4, b-BaB

2O

4 and CsLiB

6O

10 from phosphate

and borate fluxes. Growth of large size and good optical quality crystals, in turn, required carefuloptimization of several parameters and also development of some new growth methodologies.One particularly successful development was the use of a seeding technique where the seed-liquid interface is held at a level slightly above the liquid surface by surface tension forces. Thishelps minimize the wastage of the seed and also reduces the seeding time. This technique hasbeen successfully used for the growth of KTP, b-BBO and CLBO crystals. Photograph of typicalcrystals grown at LMDDD using this approach is shown in Fig.

All the grown crystals have been characterized in detail by use of several measurements like, X-ray diffraction, optical transmission, etch pit density etc. SHG devices have also been madeusing the grown crystals and characterized for their performance. An overview of thesedevelopments made at LMDDD will be presented.

CONTRIBUTORYPAPERS

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1. PHYSICS AND TECHNOLOGY OF LASERS

1.1 A digital detection circuit for mode-locking of Ti-Sapphire laser, S.K.Mishra andC.P.Navathe, Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore452013. A digital detection circuit for monitoring the mode-locking has been set up. It workson the idea that a mode-locked laser beam has a larger spectral width compared to when it is notmode-locked. The system involves taking composite video signal of the laser spectrum from aCCD camera as input and gives a measure of mode-locking in terms of counts displayed. Thesystem has been successfully installed at Ti-Sapphire laser.

1.2 Proton Beam Writing: Fabrication of microphotonic components in SU8, PMMA,and FOTURAN, S. Venugopal Raoa, A.A. Bettiol,b and F. Wattb , aDepartment of Physics, IndianInstitute of Technology Guwahati, Guwahati 781039, Assam, bCentre for Ion Beam Applications(CIBA), Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore117542. Proton beam writing is a direct-write technique capable of creating 3-D high aspectratio nanostructures in variety of materials like PMMA, SU8, Silicon, and FOTURAN. We willdiscuss the fabrication and characterization issues of micro-lasers, waveguides, and other photoniccomponents in this presentation.

1.3 Diode Pumped High Power Nd:YAG Laser Transmitter, Chitra Mishra,K.C.Bahuguna, N.S.Vasan and S.P.Gaba, Instruments Research & Development Establishment,Dehradun – 248008. This paper presents the design and development of a diode-pumped electro-optically Q-switched high power Nd:YAG laser transmitter operating at 1Hz/20Hz with anoptical efficiency of 15%. The transmitter produces 85 mJ energy in 17 ns pulses, correspondingto 5 MW peak optical power, with a beam divergence of 0.3mrad. It has been integrated with anindigenously developed prototype laser system for ranging applications.

1.4 Concentration effects on emission yield for Laser grade dye - Rhodamine B,Amitansu Pattanaik and Gobardhan Lal, Laser Science and Technology Centre, DRDO, MetcalfeHouse, Delhi-110054. In this paper Rhodamine B was studied in methanol and water withdifferent concentration and it was found that 10-4M concentration solution was effective forlaser applications.

1.5 94 Watt compact and efficient advanced copper vapor laser (KE-CVL) system.B Singh, V V Subramaniam, SR Daultabad and A Chakraborty, Laser System EngineeringDivision, RRCAT, Indore-452013. A compact highly efficient KE-CVL is demonstrated with94 Watt average output power. The discharge tube bore diameter was 58 mm and length of ~1450 mm. The KE-CVL require about 7 kW input power switched by thyratron based modulator.The CVL require about 0.8 h for establishing threshold lasing and thereafter about 0.7 h forachieving maximum power. The wall plug efficiency of the KE-CVL was about 1.4 %.

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1.6 Development of Semi-Sealed Off Copper Bromide Laser operating on Single-PhaseAir Cooled Solid State Pulsed Power Supply, R.K.Mishra, Itisri K. Nayak, S.V. Nakhe andJ.K.Mittal, LSED, RRCAT, Indore - 452013. Copper bromide laser is a low temperature variantof copper vapour laser operating around 550°C resulting in shorter warm up time (15min) andcheaper discharge tube material (fused silica). A single phase air cooled solid state pulsed powersupply & discharge tube with side arms and discharge limiting ring apertures was developed.The power supply was designed using IGBT switch and indigenously developed ferrites tooperate at 20kHz pulse repetition rate. The average laser power obtained was 1.5W, whichgives power density of 17mW/cm3, similar to CVL.

1.7 Spatial beam profile characteristic of chirped pulse amplification based Nd:glasstable top terawatt laser system, R.K.Patidar, A.K.Sharma, M.Raghuramaiah, R.A.Joshi,P.A.Naik, and P.D.Gupta, Laser Plasma Division, Raja Ramanna Centre for AdvancedTechnology, Indore 452 013. In this paper, we present measurements of near field and far fieldspatial beam profiles at different locations of an in-house developed chirped pulse amplificationbased Nd:glass table top terawatt laser system. The effect of thermal load on the beam spatialprofile and pointing stability has been studied experimentally.

1.8 Study on the coupling of radiation in a dye laser resonator, Nidhi Sharma,Nageshwar Singh* and Sneh Lata Goyal, Department of Applied Physics, Guru JambheshwarUniversity, Hisar- 125001, Haryana, *Raja Ramanna Centre for Advanced Technology,Indore – 452013. In this paper, we have studied the effect of optical components, involved as apart of the resonator of dye laser. In high gain dye laser where losses are very high outputcoupler transmission coefficient has been optimized for maximum power. Maximum outputpower has been observed in 70 – 80 % transmission range, which is very close to the estimatedone.

1.9 Beam characteristics of a copper HyBrID laser, R. Biswal, I. K. Nayak and J.K.Mittal, Laser Systems Engg. Division, RRCAT, Indore-452013. Beam characteristics of boththe radiation components (green & yellow) of a 5cm bore and 140cm active length Cu:HyBrIDlaser (a low temperature variant copper laser) with plane plane (PP), concave plane stable (SR)and on axis positive branch unstable resonators (PBUR) of M=15 are reported. The near fieldprofiles were quasi-Gaussian and the beam widths were 2.5 to 3 cm. Pulse averaged divergencesof the green and the yellow were almost equal for PP and SR, but in case of the PBUR thedivergence of the green is more than that of the yellow. Near DL divergences (2- 4.6 xDL) areobtained in case of the PBUR M15.

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1.10 Realization of a 2.5 Watt Diffraction - limited Narrow Line-width All-fiberYb-doped CW Fiber Laser, B. N. Upadhyaya, Usha Chaturvedi, Antony Kuruvilla and A.K.Nath, Solid State Laser Division, Raja Rammana Centre for Advanced Technology, Indore-452 013. We report on the realization of a 2.57-Watt diffraction-limited narrow line-width all-fiber fiber laser in which an intra-core fiber Bragg grating (FBG) mirror has been used as rearresonator mirror and 4% Fresnel reflection from other fiber end acts as output coupler. Since nobulk mirrors have been used for resonator, there is no scope for resonator misalignment andmakes the laser to have all-fiber nature. With this fiber laser configuration, an optical-to-opticalslope efficiency of 24.3% has been achieved and out put laser spectrum has been observed tohave a peak at 1093.18 nm with an FWHM line-width of 0.18 nm.

1.11 Studies on the interference fringe stability formed by a bi-prism and UV beams ofvarying spatial coherence width generated from SHG of CVL radiations, R. Mahakud,O. Prakash, S. K. Dixit, S. Gurram1, H. S. Vora and U. Nundy, LSED, SSLD1 RRCAT Indore-452013. In this paper, we report the effect of spatial coherence on the stability of interferencefringe formed by the using UV beams of varying spatial coherence width. These UV beams aregenerated from non-linear frequency conversion of copper vapour laser with different resonators.Stability of the interference fringes is measured with a bi-prism of 20 angles. The maximumstability is observed for the UV beam having high spatial coherence.

1.12 Diode-end-pumped, conduction cooled Nd:YAG slab laser, K.Ranganathan, P. Misra,P. Hedaoo and A.K.Nath, Solid-State Laser Division, Raja Ramanna Centre for AdvancedTechnology, Indore-452 013. We report the design and performance of conduction cooled,diode-end-pumped CW Nd:YAG slab laser. Cylindrical lens duct coupled diode laser stack wasused as a pump source. Conduction cooling of the slab was achieved by water circulatedmicrochannel based copper heat sinks. The multimode laser operates at 180W with 42.3% slopeefficiency.

1.13 Electronic Control Unit for Optical Parametric Chirped Pulse Amplification(OPCPA) based Laser System, B.Singh, M.S. Ansari and C.P. Navathe, Raja Ramanna Centrefor Advanced Technology, Indore-452 013. An electronic control unit has been developed forproposed OPCPA based laser system to synchronize output laser pulses of a pump oscillatorand commercial femtosecond (fs) laser oscillator with sub-ns accuracy. The control unit usesvoltage pulse train, synchronized with output laser pulse train of fs-laser oscillator, to generatesynchronized trigger signals. These trigger signals control the operation of pump oscillator togenerate synchronous laser pulse from pump oscillator. The control unit has been tested forfeasibility of OPCPA scheme.

NLS-6 46

1.14 Pulse parameter studies in a combined end-pumped Nd:YVO4 and side-pumpedNd:YAG Q-switched laser, P.K. Mukhopadhyay, Harsita Sharma1, S.K.Sharma, K. Ranganathanand A. K. Nath, Solid State Laser Division, Raja Ramanna Centre for Advanced Technology,1M.Tech project trainee, D.A.V.V. Indore. In this paper we describe, to the best of our knowledge,the first experimental studies on a combined end-pumped Nd:YVO

4 and side-pumped Nd:YAG

laser under repetitive Q-switching configuration. We observed that pulse parameters of Nd:YAGlaser are significantly influenced by the emission from Nd:YVO

4 crystal leading to a sharp Q-

switched pulse with a high peak power.

1.15 Efficient generation of 100W green laser beam by intracavity frequency-doublingin a diode side-pumped Q-switched Nd:YAG rod laser, S. K. Sharma, P. K . Mukhopadhyay,P. Hedaoo, K. Ranganathan and A. K. Nath, Solid State Laser Division, Raja Ramanna Centrefor Advanced Technology, Indore-452 013. In this paper we demonstrate more than 100 W ofaverage green power with more than 18% optical to optical conversion efficiency using twodiffuse reflector based pump head and high gray track resistant KTP crystal for intracavityfrequency doubling. The laser was Q-switched by two AO modulators at 17 kHz repetition rate.The pulse width isa 200 ns. More than 50% of the fundamental output power with optimumcoupling was converted to green beam.

1.16 A Repetitively Pulsed Pulser-sustainer Transversely Excited CO2 Laser,N.S.Benerji, N.Varshnay, K.K.Sarangapani, L.Abhinandan and U. Nundy, RRCAT, Indore-452 013. In this paper, we report the development of an industrial version of high repetition ratepulser sustainer Transversely Excited CO

2 laser. Here, we are able to achieve pulses with energy

of 500 mJ at 70 Hz with pulse duration of 7 µSec (FWHM). The laser operates reliably aforestated energy for a period of nearly half an hour. The present operating period is good enoughfor many applications. The laser is driven by all solid-state exciter.

1.17 Development of an Electronically Controlled Fiber-optic Port Selection Techniquefor High Power Solid-State Lasers, S.C. Vishwakarma, B.N. Upadhyaya, S.K. Sah, AmbarChoubey, D. K. Agrawal, R.K. Jain and A. K. Nath, Solid State Laser Division, Raja RammanaCentre for Advanced Technology, Indore 452 013. Fiber coupled solid-state lasers have beenfound to be extremely useful for non-contact material processing applications in harshenvironmental conditions due to its flexibility and ease in handling. A single laser system canbe more useful by having multi-port time-shared or energy-shared fiber optic beam delivery. Wereport on the development of an electronically controlled fiber port selection technique for highpower solid-state lasers. This technique has been devised and implemented for port selection ina 5kW peak power Nd:YAG laser system having two fiber optic ports of 400 mm core diameterand a direct beam delivery port working on time sharing basis.

NLS-6 47

1.18 Performance of a High Power Transverse Flow CO2 Laser with a Super-GaussianGraded Phase Mirror Resonator, A K Biswas1, S V Ramagopal 2, S Kumar 2, M S Bhagat1,C H Prem Singh1 and A K Nath 1, 1. ICL Section, RRCAT, Indore -452013. 2 C.S.I.O, Chandigarh.A super-Gaussian graded phase mirror (GPM) resonator has been designed for a high power,transverse flow CW CO

2 laser using diffraction formulation. The GPM has been fabricated in

single point diamond turning machine. Experiments carried out in a high power CO2 laser with

this resonator produced a super-Gaussian output beam with more than 2 kW power. Characteristicpropagation of the super-Gaussian beam in the near-field has been studied experimentally andcompared with the numerically computed propagation. Experimental measurement of the far-field distribution has also been done.

1.19 A 50J Thyratron based Pulsed Power Supply for Transversely ExcitedAtmospheric CO2 Laser, T. Reghu, J. S. Pakhare, V. Mandloie, C. Gupta, S. Sheth and A. K.Nath, Industrial CO

2 Laser Section, Raja Ramanna Centre for Advanced Technology, Indore –

452013. In this paper we report the development of a 50J Thyratron based pulsed power supplyfor Transversely Excited Atmospheric (TEA) CO

2 Laser. The capacitor charging power supply

is the primary source for pulsed power supply which operates from 440VAC, 50Hz and it chargesa 4.5µF capacitor to 5kV within 4ms. The stored energy is transferred to a high voltage capacitorup to 50kV using two switch forward converter followed by a step up pulse transformer within18µs. A Thyratron is used as a high power closing switch to discharge the energy from highvoltage capacitor to the laser head. Laser output energy has been stabilized by regulating theoutput of the primary energy source i.e. CCPS at low voltage level. The microcontroller basedcontrol unit controls the whole laser operation as well as provides trigger pulses to the pulsedpower supply. The pulsed power supply generates 50kV output with a rise time of less than 100nsec at 200Hz pulse repetition rate.

1.20 120 Watt compact and efficient single stage KE-CVL MOPA system, B. Singh,V.V. Subramaniam, S. R Daultabad and A. Chakraborty, Laser System Engineering Division,Raja Ramanna Center for Advanced Technology, Indore-452 013. A 120 Watt KE-CVL MOPAsystem is demonstrated with two KE-CVL units with over all wall plug efficiency of about 1.45%. The electro-optic efficiency of KE-amplifier was about 1.6 %. Laser power extracted fromamplifier was about 105 Watt with electrical input power of about 6.5 kW. Amplifier tuningcurve was about 150 ns in width.

1.21 Beam Homogenization of XeCl Excimer Laser, B.B. Shrivastava, P.Bhatnagar andU.Nundy, Chemical and Excimer Laser Section, RRCAT, Indore-452 013. Beam shaping andhomogenization is essential to a large number of material processing applications. Howeverexcimer laser emits a beam, which is multimode with intensity variations on both the axis. Theprofile is often described as ‘Quasi-Gaussian’. We have used a beam homogenizer system tosmooth out the irregularities of our XeCl laser beam and create a uniform profile. The beamuniformity achieved is ± 1.5% and ± 3.5%, with the steepness of 1.42 mm and 1.5 mm in thehorizontal and vertical direction respectively. The output optical efficiency of homogenizedbeam achieved is > 72%.

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1.22 Comparative performance studies between copper vapour and copper HyBrIDlaser, R. Biswal, P.K. Agrawal, S.V. Nakhe and J.K. Mittal, Laser Systems Engg. Division,RRCAT, Indore-452013. Temporal characteristics laser discharge voltage, current, power buildup and output optical pulses (green and yellow) as well as spatial characteristics of intensityprofiles for an elemental CVL and a Cu:HyBrID laser operating at their optimum conditions arereported. The CVL consists of 4.7cm bore diameter & 150 cm length alumina discharge tubeand the Cu:HyBrID laser consists of 5cm bore diameter and 140cm length fused silica dischargetube and both are excited using similar capacitor transfer circuit with same switching element(EEV CX 1535 thyratron).

1.23 Demonstration of 3.4mW SLM UV Laser at 266nm by Resonant Cavity Doublingof Diode Pumped Nd:YVO4/KTP Green Laser, Jogy George, Renuka Sehgal and A K Nath,Solid State Laser Division, RRCAT, Indore –452013. We have demonstrated 3.4mW of SLMUV laser at 266nm by resonant cavity doubling of SLM 532nm pump with 250mW of outputpower. Hansch-Couillaud based frequency locking scheme was used. A 7mm B-cut b-BBOwas used for 266nm generation. The SLM 532nm with 250mW of output power was generatedby intracavity doubling of a diode end pumped Nd:YVO

4/KTP laser pumped with a 1W fiber

coupled laser diode.

1.24 Miniature, tunable, helium free repetitive TEA CO2 laser for DIAL application,

Aniruddha Kumar*, J. P. Nilaya and D.J.Biswas *Advanced Fuel Fabrication Facility,BARC,Tarapur Laser and Plasma Technology Division, BARC,Trombay. We have succeeded inoperating a repetitive mini TEA CO

2 laser using helium free, high concentration CO

2 gas mixture

to obtain short duration optical pulses required for DIAL applications for monitoring tracequantities of gaseous impurities present in the atmosphere.

1.25 Switch-less operation of preionising parallel spark channels of a conventional TEACO2 laser, Pallavi Raote, Gautam Patil, M. B. Saiprasad, J. Padma Nilaya and D. J. Biswas,Laser and plasma Technology Division, BARC. In this paper we report the successfulsimultaneous closure of 12 pairs of parallel spark channels capable of holding upto a maximumvoltage of ~18kV without the usage of any extraneous switch. This switch cum preioniser,when used in conjunction with a LC inversion circuit, is, we believe, capable of driving a TEACO

2 laser of conventional volume.

1.26 Switching of a tea CO2 laser with its own UV emitting parallel spark channels,

J. Padma Nilaya, Pallavi Raote, Gautam Patil and Dhruba J. Biswas, Laser and PlasmaTechnology Division,B.A.R.C., Mumbai – 400 085. The efficient operation of a TEA CO

2 laser

wherein the parallel spark channel preioniser of the laser itself functioned as a switch is reported.Simultaneous closure of the parallel gaps without an external switch has been achieved byballasting them with mutually coupled inductances. The repetitive operation capability of sucha laser is also discussed.

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1.27 LCC Resonant Converter based power supply for high power Diode Laser,J. Khanwalkar, R. Arya and A. K. Nath, Solid State Laser Division, Raja Ramanna Centre forAdvanced Technology, Indore-452 013. In this paper, a current regulated power supply of 40A,3V based on LCC resonant converter, is presented with experimental results. It can deliveroutput current in the range of 5A to 40A, with a compliance voltage of 3 V. The operatingfrequency of the converter is in the range of 90 kHz to 180 kHz. Efficiency of the converter is77% at 40 A of load current. Line regulation of the power supply is measured to be better than0.15% at full load for a line variation of ± 10%.

1.28 Use of multiple dot mirrors in copper vapor laser stable resonator - A newcavity configuration, B Singh, S.R. Daultabad, V.V. Subramaniam,, D.V. Ghodke and AChakraborty, Laser System Engineering Division, Raja Ramanna Centre for AdvancedTechnology, Indore 452013. A new cavity configuration in a copper vapor laser is demonstratedto achieve maximum output power in low divergence angle of the output beam. Maximumoutput power of ~36 W with average beam divergence of ~ 0.12 mrad was achieved on usingclose packed 2́2 array of 4 dot mirrors in off-axis stable cavity.

1.29 Hybrid resonator for kinetically-enhanced copper vapor laser, B Singh, S.R.Daultabad, V.V. Subramaniam and A Chakraborty, Laser System Engineering Division, RRCATIndore –452013. An Off-axis hybrid resonator is demonstrated for the first time in coppervapor laser. Average beam divergence of about 0.2mrad and 0.8 mrad was obtained in unstableand stable direction respectively.

1.30 Pulsed lasers pumped by generators with inductive energy storage, V.F. Tarasenko,A.N. Panchenko and A.E. Tel’minov, Institute of High Current Electronics, SB RAS,Akademichesky Ave., 2/3, Tomsk, 634055, Russia. Laser and discharge parameters in mixturesof rare gases with halogens driven by a pre-pulse-sustained circuit technique are studied. Inductiveenergy storage with semiconductor opening switch was used for the high-voltage pre-pulseformation.

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2. LASERS IN NUCLEAR SCIENCE AND TECHNOLOGY

2.1 Studies on Laser enrichment of Oxygen -18, P. Mathi, D.N. Joshi, A.K.Nayak, S.K.Sarkar and V. Parthasarathy, Laser & Plasma Technology Division, Radiation & PhotochemistryDivision Bhabha Atomic Research Centre, Tromaby, Mumbai – 400 085. This paper reports thepreliminary results on the Infrared multiphoton dissociation of di - isopropyl ether in the contextof oxygen – 18 enrichment by IR laser chemistry.

2.2 Development of In-situ Laser Cutting Technique for High Pressure FeederCoupling Studs in Pressurized Heavy Water Reactors, B.N. Upadhyaya, S.C. Vishwakarma,R. K. Jain, Ambar Choubey, S.K. Sah, D.K. Agrawal, Sabir Ali and A.K. Nath, Solid StateLaser Division, Raja Rammana Centre for Advanced Technology, Indore-452 013. We reporton the development of a fiber coupled Nd:YAG laser based cutting technique for High PressureFeeder Coupling (HPFC) Studs in pressurised heavy water reactors (PHWR). It includes a fixturewith motorized rotation and having flexibility to accurately fix the position of cut. Thismanipulator holds the fiber-optic cutting nozzle and can be fixed on E-face of coolant channelhaving flexibility to access any of the orientations of these studs. This laser cutting techniquehas been successfully deployed for easy cutting, short time and thereby reduces MANREMconsumption during en-masse coolant channel replacement (EMCCR) at Narora Atomic PowerStation.

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3. SEMICONDUCTOR LASERS AND OPTOELECTRONIC DEVICES

3.1 Indigenous Technology Development of PI N photodiodes, Anita Topkar and AseemSingh Rawat, Bhabha Atomic Research Centre, Trombay, Mumbai-400 080. Feasibility studyfor the indigenous technology development of silicon PIN photodiodes has been carried out atBARC. The results are very encouraging and the details of fabrication process and performanceof these photodiodes are presented in this paper.

3.2 Analysis of Carrier Density and Wave function Intensity in Coupled QuantumDot system, Mangesh Patil, Ujawala Zope, Kanchan Talele, E. P. Samuel and D. S. Patil,Department of Electronics, North Maharashtra University, Jalgaon [Maharashtra]. Analysisof carrier density and wave function intensity in coupled quantum dot system using GaN hasbeen carried out using Quantum Transport Boundary Method and Transfer matrix methodrespectively. The effect of temperature and Aluminum mole fraction on the carrier density hasbeen estimated. The wave function intensity for the coupled quantum dot system has been obtainedby squaring amplitudes of wave functions. The wave functions have been deduced through thesolutions of Schrödinger equation. The carrier density has been obtained by considering carriertransition between Eigen energy states E

1 and E

2.

3..3 Studies on thermal resistance of CW GaAs-AlGaAs SQWSCH semi conductorlaser diodes, T.V.S.L. Satyavani, Deepti Jain, Amit Bhatti, S.K. Mehta and H.P. Vyas, SolidState Physics Laboratory, Delhi. In this paper, the thermal resistance, which is essential forevaluating the performance of Continuous Wave SQW SCH GaAs-AlGaAs semiconductor laserdiodes is measured by two different techniques. The relative merits of the two techniques andresults obtained are compared and discussed. Among the two techniques spectral measurementtechnique is found to be much simpler. The minimum thermal resistance measured is 9.4 oC/Wfor CW laser diodes.

3.4 Automation of Laser Diode Characterization Facility V. A. Kheraja, P. K. Patela, C.J. Panchala, and T. K. Sharmab aApplied Physics Department, Faculty of Technology &Engineering M. S. University of Baroda, Vadodara-390001 .bSolid State Laser Division, RajaRamanna Centre for Advanced Technology, Indore-452013. Fabrication of laser diodes requiresfrequent testing during different stages of its evolution from structure growth to packaging.These include measurements of L-I characteristics, I-V Characteristics, and spectral response.In order to maintain the uniformity of measurement conditions with higher precision andreliability, we have developed a virtual instrument involving the automation of laser diodecharacterization facility using LabVIEW.

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3.5 Laser diode processing using shadow mask techniques: A quick turn aroundmethod, V. K. Dixit1, Tapas Ganguli1, S. D. Singh1, S. Pal1, Ravi Kumar1, K. Alexander1, A.Kuruvilla2 , B. N. Upadhyaya2, T. K. Sharma1 and A. K. Nath1,2 , 1Semiconductor laser section,2Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore-452013.A quick method of laser diode processing has been successfully implemented using shadowmask technique. Utilizing these masks we have made laser bars for 735, 808, 853, and 965nmwavelengths and demonstrated laser with peak power ~4.5W at 1/1000 duty cycle with 1 msecpulse duration. The slope efficiency is ~0.42W/A per facet and the threshold current density ofthe laser is 350A/cm2 as measured from the L-I characteristics. The shadow mask were madeusing optimized laser cutting by a lamp pumped Q-switched Nd:YAG laser.

3.6 Studies on carrier doping of laser diode structures grown using MOVPE, V. K.Dixit, Tapas Ganguli, S. D. Singh, S. Pal, Ravi Kumar, S. Porwal, K. Alexander, T. K. Sharmaand A. K. Nath , Semiconductor laser section, Soild State Laser Division, Raja RamannaCentre for Advanced Technology, Indore- 452013. Studies on carrier doping density are carried-out in various epilayers and Laser diode structures grown using MOVPE. The ionized dopingand free carrier density were estimated from Hall and ECV experiments. The net ionized dopingwas also estimated at different depth of the laser diode structures using ECV. We coulddemonstrated lasers with ~5.2W peak power at 1/1000 duty cycle. The differential quantumefficiency is ~86% as obtained from L-I characteristics.

3.7 Processing of high power laser diode structures using photolithography and lift-off techniques, Suparna Pal, V.K Dixit, S. D. Singh, Tapas Ganguli, Ravi Kumar, S. Porwal,K. Alexander , Palika Rawat, T. K. Sharma and A. K. Nath, Semiconductor Laser Section, SolidState Laser Division, Raja Ramanna Centre for Advanced Technology, Indore – 452013. Betterundercut has been achieved in lithography process by modifying the surface with chlorobenzene.Peak power of about 2.67 W/facet has been achieved when lased under 500 ns pulse durationwith a duty cycle of 1:1000. The average threshold current density and slope efficiency of thesedevices are 367 A/cm2 and 0.56 W/A per facet respectively for single facet.

3.8 Spectroscopic Investigations of Quantum Well Laser Structures, S. Porwal, RaviKumar, T. K. Sharma, S. D. Singh, V. K. Dixit, Tapas Ganguli and A. K. Nath SemiconductorLaser Section, Solid State Laser division, Raja Ramanna Centre for Advanced Technology,Indore-452013. Quantum well (QW) laser structures meant for operation at about 810 nm areinvestigated through spectroscopic techniques. Strength of Surface Photovoltage Spectroscopytechnique over conventional Photoluminescence spectroscopy has been illustrated forunderstanding the QW laser structures.

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4. LASER MATERIALS : DEVICES AND COMPONENTS

4.1 Laser heated pedestal growth of the organic optical material 3-methoxy 4-hydroxybenzaldehyde, Shivani Singh and Bansi Lal, Centre for Laser Technology, Indian Institute ofTechnology Kanpur, Kanpur-208016. Crystalline fibers of 3-methoxy 4-hydroxy benzaldehyde,an organic optical material with potential to be an efficient harmonic generator of the wavelengthsfrom 700-1500nm, have been prepared from melt using laser heated pedestal growth setupassembled around a CW CO

2 laser. Using 2W CW CO

2 laser radiation 10-20mm long crystalline

fibers with diameter in 0.7-1mm range have been prepared using the sample-rod pushing- speedof 10.34cm/hr and fiber- pulling speed of 13.22cm/hr. XRD and FTR of the crystalline fibersmatch well with those of the crystals grown from the solution.

4.2 Laser heated pedestal growth of crystalline LiNbO3 crystal directly from thecongruent mixture of Li2CO3 and Nb2O5 , Sasmita Kumari Patro, Satyendra Singh Thakur,Pradeep Kumar, Bansi Lal and Joseph John, Centre for Laser Technology, Indian Institute ofTechnology Kanpur, Kanpur-208016. Crystalline fibers of LN have been grown directly fromthe congruent mixture of Li

2CO

3 and Nb

2O

5 using laser heated pedestal growth technique using

~25W of CW CO2 laser radiation, 2.7cm/hr sample rod pushing speed and 3.96 cm/hr crystalline

fiber pulling speed. Powder XRD of this fiber matches very well with that of the LN preparedby solid state reaction. Optimization of various experimental parameters to obtain the best possiblecrystalline LN fibers is reported.

4.3 UV-VIS-IR absorption of Methylene Blue encapsulated in silica matrix, UmeshGupta, S.K. Ghoshal, K.S. Gill and D. Mohan, Department of Applied Physics, GuruJambheshwar University, Hisar-125001. The absorption spectra of Methylene Blue (MB) dyeis investigated in the glassy matrix. Concentration dependence of absorbance and peak wavelengthshows abnormal behavior at some particular points. This paper emphasizes on those particularpoints. Absorption spectra for both UV and Visible region have some similar and some reversetrends, which may lead to some fruitful results for further investigations.

4.4 Optical absorption and photoluminescence properties of Er3+ doped mixed alkaliborate glasses, Y.C. Ratnakaram, A. Vijaya Kumar, D. Tirupathi Naidu and R.P.S. Chakradhar,S.V. University P. G. Centre, Kavali-524 201, A.P, 1CGCRI, Calcutta-700032. Optical absorptionand fluorescence spectra of 0.2 mol% Er

2O

3 in mixed alkali borate glasses of the type xLi

2O.(32-

x)Na2O-67.8B

2O

3- 0.2 Er

2O

3,xLi

2O.(32-x)K

2O -67.8B

2O

3-0.2 Er

2O

3 and x Na

2O.(32-x)K

2O-

67.8B2O

3-0.2 Er

2O

3 (where x=8, 12, 16, 20 and 24) are studied. The glasses were obtained by

quenching melts consisting of H3BO

3, Li

2CO

3, Na

2CO

3, K

2CO

3 and Er

2O

3 (950-11000C, 1.5-2h)

between two brass plates. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (W2, W

4 and

W6) are obtained. Radiative and non-radiative transition rates (A

T and W

MPR), radiative lifetimes

(tR), branching ratios (b) and integrated absorption cross sections (å ) have been computed for

certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have beenstudied for all the three Er3+ doped mixed alkali borate glasses. From the above studies, certaintransitions are identified for laser excitation.

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4 5 Absorption and emission properties of Sm3+ ions in mixed alkali borate glasses,D. Thirupathi Naidu, A. Vijaya Kumar, A.V. Reddy1 and Y.C. Ratnakaram, Department of Physics,S.V. University P.G. Centre, Kavali-524 201, A.P, 1Department of Physics, J.B. Degree College,Kavali-524 201, A.P. The present work aims to study the variation of Judd-Ofelt intensityparameters, radiative transition probabilities, absorption and emission cross sections with alkalicontent in three different Sm3+ doped mixed alkali borate glasses. Mixed alkali borate glasses inthe composition 67H

3BO

3.xLi

2CO

3.(32-x)Na

2CO

3.1Sm

2O

3, 67H

3BO

3.xLi

2CO

3.(32-

x)K2CO

3.1Sm

2O

3 and 67H

3BO

3. xNa

2CO

3.(32-x)K

2CO

3.1Sm

2O

3 with x=8, 12, 16, 20 and 24

mol% were prepared by quenching melts. Judd-Ofelt theory is used to study the spectral propertiesand to calculate the radiative transition probabilities and branching ratios. The predicted radiativetransition probabilities (A), branching ratios (b) and integrated absorption cross sections (å )for certain transitions are reported. From the emission spectra, emission cross sections (s

P) are

obtained for the four transitions, 4G5/2

® 6H5/2

, 4G5/2

® 6H7/2

, 4G5/2

® 6H9/2

and 4G5/2

® 6H11/2

of Sm3+

ion in these mixed alkali borate glasses. From the above studies, certain lasing transitions areidentified.

4.6 Laser Induced Photo-physical properties of Rhodamine 6G encapsulated inTetramethylorthosilicate, Sunita Sharma, D. Mohan, S. K. Ghoshal, Nageshwar Singh*andH.S.Vora* Dept. of Applied Physics, Guru Jambheshwar University, Hisar-125001, Haryana,*Dept. of Atomic Energy, Center of Advanced Technology, Indore-452 013. In the presentwork, concentration dependent studies of peak lasing wavelength, full width at half maxima(FWHM) and bleaching effect in Rhodamine6G doped glassy material is investigated underhigh repetition rate of Copper Vapor laser at 510.6nm.

4.7 Energy transfer in the Tb3+:Eu3+ system in sol gel matrix, Jyothy P V, Amrutha K A,Gijo Jose, Rejikumar P R and N V Unnikrishnan School Of Pure & Applied Physics, MahatmaGandhi University, Kottayam, Kerala. Sol –gel silica glasses containing rare earth materials area matter of great interest for the materials scientist due to their sharp emission bands. Opticalcharacteristics of rare earth doped glasses for laser applications are greatly dominated by thespectroscopic properties of the ions doped in it. Europium (Eu3+) is well known and most usedRED phosphor. Terbium (Tb3+) is mostly used for the green emission application. Here wereport the enhancement of the RED luminescence from Eu3+ ions in the presence of Tb3+ ions.This is discussed based on the energy level diagram of these rare earth ions.

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4.8 Investigation of Optical Properties of Dyes doped KDP crystals, P.Kumaresan1,2

and S.Moorthy Babu1, 1 Crystal Growth Centre, Anna University, Chennai-600 025, 2 Departmentof Physics, Adhiparasakthi Engineering College, Melmaruvathur-603 319. The organic dyes(Amaranth, Rhodamine and Methyl Orange) are doped in KDP crystals. Influences ofsupersaturation and dye concentration in the solution were observed on the color and crystalhabit of KDP. Amaranth colored the pyramidal section (321) of the crystals in the solution atlow super saturation and high dye concentration. Influences of supersaturation and dyeconcentration in the solution were observed on the color and crystal habit of KDP. Amaranthcolored the pyramidal section (101) of the crystals in the solution at low super saturation andhigh dye concentration. The highly super saturated solutions produced entirely colored crystals.The grown crystals were characterized by employing UV-Visible Spectrum, FT-IR & X-Raydiffraction methods. The doped crystals show good second harmonic generation efficiency.

4.9 Preparation and Characterization of Nd3+ doped multilayed sol-gel silica thin filmswith low H 2O:TEOS ratio, Rejikumar P R, Jessyamma Kurian, Xavier Joseph, Siby Mathewand N V Unnikrishnan, School of Pure & Applied Physics, Mahatma Gandhi University,Kottayam, Kerala. Multilayed Neodymium doped solgel silica thin films were dipcoated fromthe sol prepared with water : alkoxide ratio of 0.5, 1 and 2. Structural characterization wascarried out with the FTIR, the broad vibration band from 3000cm-1 to 4000cm-1 was deconvolutedto reveal the relative silica and water content. The Absorption spectra of the films shows theabsorption peaks corresponding to the Neodymium ions and from the emission spectracharacteristic emssion peak around 1060nm was obtained.

4.10 Growth and characterization of the Tri-allylthiourea complex NLO crystals: Tri-allylthiourea Cadmium Bromide and Tri-allylthiourea Mercury Bromide, R.Perumal andS.Moorthy Babu,Crystal Growth Centre, Anna University, Chennai 600 025. Growth of tri-allylthiourea complex NLO crystals: tri-allylthiourea cadmium bromide(ATCB) and tri-allylthiourea mercury bromide(ATMB) single crystals by solvent evaporation technique hasbeen carried out. The powder SHG efficiency of these crystals is as high as that of urea. Thefunctional group, defect studies and optical properties of the grown crystals were analyzedthrough FT-IR, chemical etching and UV-visible absorption studies. The applicability of thematerials for NLO devices was analyzed.

4.11 Growth and Characterisation of PbMoO4 Single Crystal for Acousto-Optic DeviceApplications, G. Madeswaran and R. Dhanasekaran, Crystal Growth Centre, Anna University,Chennai – 600 025. Growth of PbMoO

4 single crystals used for acousto-optic device applications

has been carried out by Czochralski crystal pulling technique. The dimension of the crystal is 2cm diameter and 1.5 cm thickness. The grown crystal has been subjected to powder XRDanalysis and the results are discussed.

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4.12 Synthesis of CuAlS2 Nanocrystals by Wet Chemical Method, P.Prabukanthan1,G. Harichandran2 and R. Dhanasekaran1, 1Crystal Growth Centre, Anna University, Chennai2Department of Polymer Science, University of Madras, Guindy Campus Chennai-600 025.Chalcopyrite ternary semiconductor CuAlS

2 nanocrystals were successfully prepared via a wet

chemical method. Form powder XRD, the lattice constants a and c have been determined. Thesample CuAlS

2 was characterized by scanning electron microscope (SEM) and optical absorption

spectrum.

4.13 Growth of Yttrium Calcium Oxy Borate (YCOB) Single Crystals for NonlinearOptics, R. Arun Kumar, M. Senthilkumar and R. Dhanasekaran, Crystal Growth Centre, AnnaUniversity, Chennai–600 025. Yttrium Calcium Oxy Borate (YCOB) single crystals have gainedattention in Nonlinear Optics. Also, YCOB is an efficient laser host material. YCOB wassynthesized by solid state reaction technique. For the first time, the flux technique was adoptedto grow YCOB single crystals, using Li

2CO

3 flux and tiny YCOB single crystals were obtained.

The XRD, DTA and TG studies were performed and the results are presented.

4.14 Not Assigned.

4.15 Domain wall width of VTE treated near stoichiometric LiNbO3 crystal, S. Kar andK. S. Bartwal, Laser Materials Development & Devices Division, Raja Ramanna Centre forAdvanced Technology, Indore–452013. The high performance of lithium niobate, LiNbO

3 (LN)

crystal as an electro-optic, photo refractive, piezoelectric, and nonlinear optical crystals, makeit useful for many different applications. The sample is etched in the mixture of HF and HNO

3

and the domain wall were measured in optical microscope. Measured domain wall width wasfound approximately 1-3 µm range. The reasons for reduction in domain wall size will bediscussed.

4.16 Theoretical coercive field of MgO doped LiNbO3 crystal, N. Sisodia1, S. Kar3,P. Sen2 And K. S. Bartwal3, 1Department of Physics, Holkar Science, College, Indore- 452 017.2Department of Applied Physics, SGSITS, Indore-452 003, 3Laser Materials Development &Devices Division, Raja Ramanna Centre for Advanced Technology, Indore-452 013. Model hasbeen proposed to calculate coercive field of undoped and Mg doped LiNbO

3 crystals. This

model calculates the accurate value of coercive field of congruently grown LN and MgO dopedLN. In order to substantiate our results we also measure the activation energy of the crystal asa function of MgO doping concentration.

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4.17 OH- ion spectroscopy of Mg:Nd:LiNbO3 single crystal, R. K. Choubey1, P. Sen1,S. Kar2, B. Q. Khattak3, P. Ramshankar3 and K. S. Bartwal2, 1Department of Applied Physics,SGSITS, Indore - 452 003, 2Laser Materials Development & Devices Division, Raja RamannaCentre for Advanced Technology, Indore – 452 013, 3Chemical Treatment Facility, Raja RamannaCentre for Advanced Technology, Indore – 452 013. Infrared optical absorption has been usedto study the impurities concentration in the grown crystals. The OH – ion peak position is thedirect consequence of presence of impurities in the crystal. The shift in OH – peak position isused to correlate the Li/Nb ratio in the crystal.

4.18 Effect of oil vapour contamination on the performance of porous silicaantireflection coatings on optical glass blanks used in high power Nd:glass lasers, M.N.Kumbharea, R. Pareeka, A. S. Joshia, C. Mukharjeeb, Rajeev Kb, P. D. Guptaa , aLaser PlasmaDivision, bLaser System Engineering Division Raja Ramanna Center for Advanced Technology,Indore-452 013. We report the studies on the degradation of the single layer silica sol-gel anti-reflection (AR) coated optics used in the vacuum spatial filters due to it’s exposure to the rotaryvacuum oil vapours causing increase in the reflectivity of the AR coating and the decrease inlaser induced damage threshold. The degradation was minimal on treatment of the coated opticswith hexa-methyl di-silazane (HMDS) Vapours.

4.19 Growth and Structural Analysis of a Novel Organic NLO Crystal : Paranitrophenol, C. Vesta, R. Uthrakumar, C. Justin Raj, G. Mangalam1 and S. Jerome Das,Department of Physics, Loyola College, Chennai-600 034, 1Department of Physics, Dr. M. G.R Educational and Research Institute, Madhuravoyal, Chennai-600 095. Good quality crystalsof p-nitrophenol have been successfully grown by slow evaporation method. The structuralanalysis of the crystal is determined using X-ray diffraction method. The non linear opticalactivity has been confirmed by Kurtz powder technique.

4.20 Studies on ADP and ADP Mixed Crystals, R.Robert1, C.Vesta, C. Justin Raj, S.Dinakaran , S. Jerome Das, 1Dept of Physics , St Joseph’s College,Cuddalore - 607 001Department of Physics, Loyola College, Chennai-600 034. Large single crystals of ADP, ADPmixed ammonium sulphate and ADP mixed ammomiun carbonate were obtained from waterby slow evaporation technique. UV absorption spectrum had been taken on the above samplesand the FTIR spectral analysis was carried out on these samples to confirm the presence offunctional groups. The Non Linear Optical activity has been confirmed using Kurtz’s powdertechnique.

4.21 Studies On Potassium Dihydrogen Phosphate Binary Systems, R. Uthra Kumar,C. Vesta, J. Mary Linet, S. Dinakaran and S. Jerome Das, Department of Physics, LoyolaCollege, Chennai –600 034. Single crystals of KDP, KDPOP acid binary systems were grownby solution growth technique. FTIR measurements on these crystals confirm the presence offunctional groups. The UV optical absorption studies were carried out on the grown crystals toconfirm the possibility towards device fabrication.

NLS-6 58

4.22 Crystal growth, optical and thermal studies on a novel amino acid crystal forNLO applications, C. Justin Raj1, G. Mangalam2, B. Milton Boaz3, R. Uthrakumar1, S. JeromeDas1, 1Department of physics, Loyola College, Chennai- 600 034, 2Department of Physics, Dr.M. G. R Educational and Research Institute, Madhuravoyal, Chennai-600 095, 3Department ofphysics, SRM Institute of Science and Technology, Kattankulathur, Chennai. Good optical qualitysingle crystals of L-alanine formate (L-AlFo) have been grown from aqueous solution by slowevaporation technique. Single crystal X-ray analysis confirms that the crystal belongs toorthorhombic structure with space group P2

12

12

1. The presence of formate functional groups in

L-AlFo were confirmed by FTIR analysis. The nonlinear optical property of the grown crystalwas confirmed by employing Kurtz powder test. The DRS UVvisible spectrum of the crystalshows that the crystal has UV cut off at 205 nm. TGA / DTA reveals that the crystal is thermallystable up to 234º C.

4.23 Growth and characterization of gel grown single crystal of ZnHPO4 , G. Mangalam1,

C. Justin Raj2, S. Krishnan2, S. Mary Navis Priya2 and S. Jerome Das2, 1Department of Physics,Dr. M. G. R Educational and Research Institute, Madhuravoyal, Chennai – 600 095. 2Departmentof Physics, Loyola College, Chennai–600 034. Good optical quality single crystals of zinchydrogen phosphate (ZnHPO

4) have been grown with the aid of sodium meta silicate gel. Single

crystal XRD studies confirm that the crystal belongs to the orthorhombic system with spacegroup P2

12

12

1. The functional groups present in the crystal was confirmed using FTIR technique.

Optical absorbance shows very low absorption in the entire visible region. Differential thermaland thermo gravimetric analysis confirmed that the crystal is stable up to 193 ºC.

4.24 Growth, optical, microhardness and thermal studies on NPNaLi: A novelsemiorganic NLO material, B. Milton Boaz1, C. Justin Raj2, J. Mary Linet2 , S. Mary NavisPriya2, C. Vesta2 and S. Jerome Das2, 1Department of Physics, SRM institute of Science andTechnology, Kattangkulathur – 603 203. 2Department of Physics, Loyola College, Chennai –600 034. Lithium p-nitrophenolate trihydrate (NPLi.3H

2O) is a potential semiorganic NLO

crystal possessing large value of molecular hyperpolarizability and SHG efficiency. Hence itcan be used for NLO and photonic devices. In the present work, a new crystal sodium substitutedlithium p-nitrophenolate (NPNaLi.3H

2O) was obtained by slow evaporation technique. It is

observed that the NLO property of NPNaLi is found to be doubled in comparison with NPLi.This is due to the active charge transfer protoniation of less electronegative sodium ions in thelattice of NPLi through CT axis. The crystal is also subjected to thermal, microhardness anddielectric studies and the results are discussed in detail.

4.25 Studies on the non linear optical L -Threonine single crystals, J. Mary Linet,S. Mary Navis Priya, S. Dinakaran, S. Krishna and S. Jerome Das, Department of Physics,Loyola College, Chennai – 600 034. Single crystals of l-threonine were successfully grownslow solvent evaporation technique. The grown crystals were characterized by single crystalXRD and the functional groups have been identified by FTIR spectrum.The crystals possesswide optical transmission in the visible region.

NLS-6 59

4.26 Growth and characterization of the non linear optical ã-Glycine crystal, S. MaryNavis Priya, J. Mary Linet, R. Robert, C. Vesta and S. Jerome Das, Department of Physics,Loyola College, Chennai – 600 034. Bulk crystals of ã-glycine have been grown at ambienttemperature of 40 °C by solvent evaporation from solvent mixtures of water and hydrogenfluoride. The ã-phase was confirmed by single crystal XRD. The absorption wavelengths werefound by UV absorption studies. The crystal shows positive photoconductivity.

4.27 Studies on NLO active Hippuric acid single crystals, S. Dinakaran, J. Mary Linet,S. Mary Navis Priya, R. Uthrakumar, S. Jerome Das, Department of Physics, Loyola College,Chennai – 600 034. The organic nonlinear optical crystal Hippuric acid (HA) is an excellentcandidate for second harmonic generation because of its high conversion efficiency. The HAcrystals were grown in the solvents of acetic acid and acetone using slow evaporation technique.The grown crystals were characterized by powder XRD and dielectric studies.

4.28 Extinction coefficient of stilbene-3 in Sol-Gel Matrix, Aparna V. Deshpande andLaxman V. Jathar, Physics Department, University Institute of Chemical Technology, Matunga,Nathalal Parikh Marg, Mumbai-400 019. Stilbene-3 (STB-3) impregnated sol-gel samples havebeen prepared using two different methods– mentioned as the dope and dip methods. Acomparative study of absorption properties of these STB-3/sol-gel glass materials with STB-3dye in Methanol has been reported. STB-3/sol-gel glass samples prepared by dope method arefound to have the best performance and may be useful as laser active material in solid state dyelasers.

4.29 Growth and thermal studies of a novel NLO crystal: ATCC, Ginson.P.Joseph,K.Rajarajan*, M.Vimalan, Preema C. Thomas, S.Selvakumar+, S. M. Ravi Kumar andP.Sagayaraj, Department of Physics, Loyola College, Chennai-600034. * Department of Physics,R.V.Govt.Arts Colege, Chengalpattu-603 001 +Department of physics, Sathyabama DeemedUniversity, Chennai –600119. Single crystals of ATCC with dimension up to 14x14x6mm3

were grown from aqueous solution by slow solvent evaporation method. ATCC belongs totrigonal structure with space group R

3c. The thermal properties of ATCC were studied using

TG/DTG analyses. It is evident from the thermal studies that the decomposition of the samplebegins around 200oC.

4.30 Mechanical and photopyroelectric studies of allylthiourea cadmium chloride,Ginson.P.Joseph, J. Philipa, M.Vimalan, Preema C. Thomas, S.Selvakumarb, K.Rajarajanc,S.M. Ravi Kumar and P.Sagayaraj, Department of Physics, Loyola College, Chennai-600034.aDepartment of Instrumentation, Cochin University of Science & Technology, Cochin 682022.bDepartment of physics, Sathyabama Deemed University, Chennai –600 011, cDepartment ofPhysics, R.V.Govt.Arts College, Chengalpattu-603 001. Allylthiourea cadmium chloride (ATCC),a promising non-linear optical material was grown from aqueous solution by slow evaporationtechnique. The thermal properties of ATCC were studied using photopyroelectric technique.The microhardness test conducted on the grown crystal suggests that ATCC has a relativelyhigh mechanical strength.

NLS-6 60

4.31 Growth and Photopyroelectric study of manganese mercury thiocyanate,Ginson.P.Joseph, J. Philipa, S.A.Rajasekarb, A. Joseph Arul Pragasamc, K.Rajarajand, S. M.Ravi Kumar and P.Sagayaraja Department of Instrumentation, Cochin University of Science &Technology, Cochin – 682 022. bDepartment of physics, Vellore Institute of Technology, Vellore-632 014. C Department of physics, Sathyabama Deemed University, Chennai-600 119 d

Department of Physics, R.V.Govt.Arts Colege, Chengalpattu-603 001 Department of Physics,Loyola College, Chennai-600034. A novel non-linear optical single crystal of ManganeseMercury Thiocyanate (MMTC) was grown at room temperature by slow evaporation technique.The sample was confirmed by single crystal XRD. The SHG efficiency and laser damage thresholdstudies confirm the superiority of this crystal over conventional laser materials. The thermalproperties of the crystal were investigated by photopyroelectric (PPE) technique

4.32 Growth, electrical and mechanical properties of MMTD single crystals, GinsonP.Joseph, K. Rajarajan, I.Vetha Potheher, S.M. Ravikumar, Preema C.Thomas, J.Madhavanand P. Sagayaraj Department of Physics, Loyola College, Chennai-600 034. Manganese mercurythiocyanate bis dimethyl sulfoxide (MMTD), a novel organo-metallic non-linear optical crystalwas grown by slow evaporation technique over a period of 30 days. The second harmonicgeneration (SHG) efficiency of the sample was measured using a Q-switched, mode-lockedNd:YAG laser . The dielectric response and mechanical properties of MMTD have also beeninvestigated and reported.

4.33 On optoelectronic properties of MgxZn1-xO thin films, D. Basak and R. Ghosh,Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur,Kolkata-700032. We have studied the optical absorption and photoconducting properties ofMg

xZn

1-xO (x=0.0 to 0.1) thin films deposited on glass substrate by sol-gel technique. All the

films are of hexagonal wurtzite structure. The excitonic nature of the absorption spectra isclearly visible for x=0.0, 0.03 and 0.05 indicating good optical quality of the films. Thephotoconducting properties of Mg

xZn

1-xO thin films are better around the composition x=0.05

to 0.08.

4.34 Growth and characterization of L-lysine monohydrochloride dihydrate singlecrystals, S. K. Sharma, Yeshpal Singh and K. S. Bartwal, Laser Materials Development &Devices Division, Raja Ramanna Centre for Advanced Technology, Indore-452013. TransparentL-lysine monohydrochloride dihydrate single crystals are grown (size up to 31x25x25mm3) byplatform technique from aqueous solution. The average growth rates along <011> and <100>were 5-11mm/day. Grown crystals were characterized by x-ray powder diffraction technique.Optical quality was determined by transmission spectra along <100> and <011> crystallographicdirections showing transmission as high as 80% in the visible region with lower cut off ~ 230nm.

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4.35 Photoluminescence studies of LiTaO3 thin film, S. Satapathy, Shailendra Kumarand P. K. Gupta, LMD&DD, RR Centre for Advanced Technology, Indore-452013. Lithiumtantalate (LiTaO

3) thin films have been grown on Pt-Si [Pt(111)/SiO

2/TiO

2/Si(100)] substrates.

In our PL studies on LiTaO3 we found both luminescence peaks due to band gap and sub band

gap levels. The broad background peak between 250nm to 290nm corresponds to band gap ofLiTaO

3. The band gap is not very sharp. Few sharp peaks superimposed on broad peak have

been also observed.

4.36 Single crystal growth and photopyroelectric spectroscopy of LiTaO3 , Indranil

Bhaumik, Shailendra Kumar, S. Ganesamoorthy, A.K. Karnal and P.K. Gupta LMD&DD, RRCentre for Advanced Technology, Indore-452013, B.N. Raja Sekhar Spectroscopy Division,BARC, Mumbai-400085. V. K. Wadhawan, Solid State Physics Division, BARC, Mumbai-400085.In this work, we have studied the PPE spectroscopy of congruent lithium tantalate (LiTaO

3, LT)

single crystal. The crystal is grown by Czochralski technique in Iridium crucible under nitrogenatmosphere in CRYSTAL 3M machine. For the PPE measurement, crystal plates of dimension8mm x 8mm x 0.4mm have been used as samples as well as sensor. For electrodes, the samplesare coated with gold in such a way that one face is partially covered, which enables the incidentlight to be absorbed in the sensor material. The PPE voltage is measured across the top andbottom electrodes using lock-in amplifier. The origin of large PPE voltage in the sub-band gapregion will be presented in the conference. To see the effect of oxygen annealing, the plate of LTis treated in oxygen atmosphere at 950oC for 16 hours. The decrease in the magnitude of PPEvoltage in the sub-band gap region clearly shows reduction in defect density after oxygenannealing.

4.37 Birefringence interferometry: a technique to determine linear thermal expansioncoefficients of anisotropic crystals, S. K. Sharma, Yeshpal Singh and Nilesh Bhange#,, LaserMaterials Developments & Devices Division,# Ultra High Vacuum Section, Raja Ramanna Centrefor Advanced Technology, Indore-452013. A simple laser based interferometric technique isdescribed to determine linear thermal expansion coefficient of anisotropic crystals along differentcrystallographic directions. It is based on the interference between ordinary and extraordinarywaves inside the crystal. Linear thermal expansion coefficient for KDP crystal along <100>direction is determined in the temperature range 35 oC to 65 oC.

4.38 Growth, spectroscopic and optical studies of Bisglycine Hydrobromide, K.Ambujam, S. R. Gomathy, Eucharistia Fatima Rani and P. Sagayaraj*, Department of Physics,Queen Mary’s College, Chennai-600004, 1Department of Chemistry, Queen Mary’sCollege,Chennai-600004, *Department of Physics, Loyola College, Chennai-600034. Singlecrystals of bisglycine hydrobromide (BGHB) are grown by slow evaporation technique andcharacterized by single crystal XRD, FTIR, optical absorption studies and NLO test. The growncrystal belongs to orthorhombic system.

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4.39 Growth, photoconductivity and magnetic properties of Tetrakis Thiourea NickelChloride single crystals, K. Ambujam, C. Dhakshayini, S. Vijayalakshmi1 and P. Sagayaraj*,Department of Physics, Queen Mary’s College, Chennai-600004, 1Department of Chemistry,Queen Mary’s College, Chennai-600004. *Department of Physics, Loyola College, Chennai-600034. Dark green transparent crystals of NTC (nickel thiourea chloride) of dimension 8 x 4x 3 mm3 are grown in a period of 45 days. Single crystal XRD shows that the crystal belongs tobody centered tetragonal symmetry class I4. Photoconductivity studies were carried out and arereported for the first time. Magnetic moment measurement was also done.

4.40 In search of zeta phase in the cation-rich (001) surface of III-V phosphides,C.Kamal, Aparna Chakrabarti and A.K.Nath, Semiconductor Laser Section, SSLD, RajaRamanna Centre for Advanced Technology, Indore-452013. We study the various reconstructionof InP and GaP (001) surfaces from first principle calculations. In this work we find that for InPand GaP in the anion–rich surface shows well known Beta2(2x4) and c(4x4) reconstructions.However, in the cation-rich case, GaP has a different behaviour than InP. While in InP a2x4mixed dimer phase has the lowest surface formation energy, GaP has a signature of stabilizedzeta (4x2) phase.

4.41 Synthesis, characterization and nonlinear optical properties of some novel chalconederivative crystals, Venkataraya Shettigara, R. Sai Santosh Kumarb, S. M. Dharmaprakash*

and D.Narayana Raob+, aDepartment of Studies in Physics, Mangalore University,Mangalagangotri, Mangalore - 574 199, bSchool of Physics, University of Hyderabad,Hyderabad. We report the studies of third order optical nonlinearity of four chalcone derivatives.The chalcone derivatives were synthesized by Claisen–Schmidt condensation method. Thesynthesis, characterization and third order nonlinear optical property of some new chalconederivative crystals that are inherently centrosymmetric unlike the usual chalcones that crystallizewith non centrosymmetry has been studied. We investigated the third order nonlinear opticalproperties of these chalcone derivatives for the first time using the fs DFWM technique. Thethird order susceptibility (|c(3) |), nonlinear refractive index (n

2), and second order molecular

hyperpolarizability of the molecules (g) are estimated and reported at 800 nm using thefemtosecond DFWM technique.

4.42 Effect of ZnO and SnO2 doping on the optical properties of SiC thin films prepared

using Pulsed Laser Deposition, Detty.A.P, Rani.J.R, and V.P.Mahadevan Pillai, Departmentof Optoelectronics, University of Kerala, Kariavatom-695 581, Kerala. Thin films of siliconcarbide has been prepared by pulsed laser deposition technique on quartz substrates in a nonreactive atmosphere. The effect of doping with ZnO and SnO

2 on the structural and optical

properties of SiC thin films were studied using Scanning electron microscopy, Transmissionelectron microscopy, photoluminescence spectroscopy and open aperture Z-scan technique etc.

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4.43 Broadband High Reflection Mirror for Tunable Dye Laser Operating in 510 to630nm waveband, A.S. Upadhyay, 1 Manoj Gaur,2 1Instruments Research & DevelopmentEstablishment, Dehra Dun, 2Opto Electronic Factory,Dehra Dun. Broad band high reflectionmirrors are used for Copper Vapor Laser (CVL) pumped Rhodamine 6G(Rh 6G) dye lasersystem. This tunable dye laser system generally works in 510 nm to 630 nm waveband. Thismirror is used at 45o angle of incidence having reflection around 99% with high laser damagethreshold. In the present work design and development of high reflection mirror coating at450angle of incidence on BK7 flat plate glass was attempted using gradual evaluation designtechnique. The optimized final design consists of 53 layers of SiO

2 / HfO

2 and the deposition

was carried out by electron gun evaporation system. The result achieved was around 99%reflection in 500 to 630nm for 450angle of incidence. This coating had excellent environmentalstability and also passed laser damage threshold of 55MW/cm2 with 30ns pulsed copper vaporlaser.

4.44 Green to UV upconversion in Er3+ doped TeO2- GeO2 - Na2O ternary glasses,Kaushal Kumar and S. B. Rai, Department of Physics, B.H.U., Varanasi – 221005. The green-to-ultraviolet upconversion fluorescence is observed in Er3+ doped TeO

2- GeO

2 - Na

2O glass on

532 nm excitation wavelength. The fluorescence bands are found at 380, 404, 410, 475, 525,550, 658 and 843 nm wavelengths. These bands are found due to the 4G

11/2® 4I

15/2, 2P

3/2® 4I

13/2,

2H9/2

® 4I15/2

, 2P3/2

® 4I11/2

, 2H11/2

® 4I15/2

, 4S3/2

® 4I15/2

, 4F9/2

® 4I15/2

and 4S3/2

® 4I13/2

transitionsrespectively. The lifetime of the 4S

3/2 state is measured and decay curve at low Er3+ concentration

shows single exponential behaviour.

4.45 A photoluminescence study of heteroepitaxial InP layers on Si substrate grownby metal organic vapor phase epitaxy, S. D. Singh, T. K. Sharma, Tapas Ganguli, V. K. Dixit,S. Porwal, Ravi Kumar and A. K. Nath, Solid State Laser Division, Raja Ramanna Centre forAdvanced Technology, Indore-452013. Photoluminescence (PL) and high resolution x-raydiffraction (HRXRD) measurements are performed to study the correlation between the effectof Si substrate treatment under different conditions and the presence of defects due to largelattice mismatch between InP layer and substrate. Defect related peaks observed in PL spectraare tentatively assigned to tilt and twist observed in HRXRD measurements.

4.46 Growth and Characterization of organic nonlinear optical L-arginine maleatedihydrate single crystals, D. Kalaiselvi, C. M. Raghavan, R. Mohankumar and R. Jayavel,Crystal Growth Centre, Anna University, Chennai– 600 025. Bulk single crystals of L-argininemaleate dihydrate (LAMD) were successfully grown from its aqueous solution by slow coolingand solvent evaporation method. The grown single crystals were characterized by X-ray powderdiffraction (XRD), UV-visible and FTIR analysis. The compound is thermally stable up to 95.8ºC.Second harmonic generation efficiency is found to be about 1.4 times that of KDP.

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4.47 Growth and characterization of CMTD single crystal for nonlinear opticalapplications, C. M. Raghavan, R. Sankar, R. Mohankumar and R. Jayavel, Crystal GrowthCentre, Anna University, Chennai-600 025. Bis(dimethyl sulfoxide) cadmium mercurythiocyanate (CMTD), an efficient nonlinear optical single crystal was grown from water:DMSO(1:3) mixed solvent by slow evaporation technique. The crystal structure was confirmed bypowder X-ray diffraction analysis. The coordination of ligands to the metal ions were confirmedthrough FTIR and Laser Raman spectroscopy studies. The NLO efficiency of the grown crystalwas studied using Kurtz powder technique and was compared with KDP and TSCCC crystals.

4.48 High-Resolution X-Ray Diffraction and Photoluminescence correlation as anaccurate and nondestructive evaluation technique for InGaAs/GaAs quantum wellstructures, Ravi Kumar, S. Porwal, T. K. Sharma, S. D. Singh, V. K. Dixit, Tapas Ganguli andA. K. Nath, Semiconductor Laser Section, Solid State Laser Division, Raja Ramanna Centre forAdvanced Technology, Indore-452013. InGaAs/GaAs quantum-well (QW) samples with varyingindium content are studied by HRXRD technique. The indium content in the InGaAs/GaAsQW were determined by simulating the rocking curves using Takagi-Taupin equations andmatching them with the experimental data. HRXRD results are further supported by PLmeasurements.

4.49 Tunable thin film fabry-perot filter, C. Mukherjee, A. Joseph and K. Rajiv, LaserSystem Engineering Division, Raja Ramanna Centre for Advanced Technology, Indore-452013.Wavelength tunable thin film F-P filters are developed. Tuning is achieved by varying the angleof incidence. Nine channels, each at an interval of 5.0 deg and FWHM of 10nm is obtained.The same is also achieved by spatially varying the spacer layer thickness along the diameter ofthe F-P filter. FWHM of 3nm and tuning of 21nm is achieved. Nine channels, starting from465nm, each separated by 2.3nm and 2mm spatially, along the direction of shutter motion.

4.50 Growth and characterization of semi-organic tetrakis (thiourea) cadmiumtetrakis (thiocyanato) zincate (TZTC) single crystal for the nonlinear optical applications,A. Bhaskaran, C.M.Ragavan, S.Venkatraj, R.Mohankumar and R. Jayavel, Crystal GrowthCentre, Anna University, Chennai-600 025. A new semi-organic nonlinear (TZTC) single crystalwas grown by the slow cooling method. The crystal structure, coordination of ligands, opticaltransmittance and SHG were confirmed through powder X-ray diffraction analysis, FTIR analysis,UV-VIS spectrum and Kurtz powder technique respectively.

4.51 Analysis of thin film based on spectrophotometric and ellipsometric measurements,K. Rajiv and C. Mukherjee, Laser System Engineering Division, Raja Ramanna Centre forAdvanced Technology, Indore-452013. Spectrophotometric and ellipsometric methods are usedto characterize thin films. Optical constants (n, k) and thickness (d) are determined, through amodel-based analysis of ellipsometric data. A computer code (ELLIP-SPECTRO ANALYSIS)based on Matrix Method is developed to theoretically calculate transmittance and reflectancespectra. These spectra are compared with the experimentally obtained spectra to find thecorrectness of optical constants and the model.

NLS-6 65

4.52 Synthesis and growth of Triaquaglycinesulfatozinc (II), [Zn (SO4) (C2H5NO2)(H2O)3] a new semi organic nonlinear optical crystals, R. Sankar, C.M. Raghavan,R. Mohankumar and R. Jayavel, Crystal Growth Centre, Anna University, Chennai-600 025. Anew semi organic nonlinear optical material, Tri aquaglycinesulfatozinc (II), [Zn (SO

4) (C

2H

5NO

2)

(H2O)

3] has been synthesized. Bulk crystal of ZGS has been grown by the slow cooling method.

The grown crystals were subjected to various characterization studies such as chemical etching,FTIR analysis, UV-visible spectrum and powder SHG test. The structure of the crystal wasconfirmed by single-crystal X-ray diffraction analysis. ZGS crystals exhibit better thermal andmechanical stability with improved optical properties.

4.53 Optical characterization of Mn-Doped Zn2SiO

4 , Poonam Sharma and H.S. Bhatti,

Department Of Physics, Punjabi University, Patiala-147 002, Punjab. Mn- doped Zn2SiO

4

nanophosphors have been prepared by using sol-emulsion-gel method. Sol was prepared byusing absolute ethanol, zinc acetate and Manganese acetate in fixed proportions. Samples werecharacterized by x-ray diffraction (XRD), which confirms the formation of pure willemite(Zn

2SiO

4) phase. Photoluminescence measurements of the Mn- doped Zn

2SiO

4 nanoparticles

show emission band at 536nm. The decay time is observed to be 5µ

4.54 Synthesis and Characterization of Colloidal ZnO nanoparticles: A novel Technique,S. C. Singh and R. Gopal Laser and Spectroscopy Lab, Department of Physics, University ofAllahabad, Allahabad-211002.

4.55 Top seeded solution growth of stoichiometric LiNbO3 single crystals, Rajeev Bhatt, S.Ganesamoorthy, Indranil Bhaumik, A.K. Karnal and P. K Gupta, Laser Materials Developmentand Devices Division, Raja Ramanna Centre for Advanced Technology, Indore- 452 013. Thegrowth of stoichiometric LiNbO

3 crystals (SLN) has been carried out by top seeded solution

growth technique (TSSG) using Li-rich melt (58.0 mol.% of Li2O). Grown SLN crystals were

characterized for powder XRD, transmission and optical microscopy. Near stiochiometriccomposition and single domain structure except at peripheries was observed.

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5. QUANTUM OPTICS

5.1 Composite Two-Photon Rabi Frequency Approach for Coherent Two-PhotonExcitation of a Three-Level Atom with an Off-Resonant Intermediate Level, G. P. Guptaand B. M. Suri, L&PTD, BARC, Mumbai–400085. Coherent two-photon excitation of a three-level atom with an off-resonant intermediate level using two counterpropagating pulsed lasersis investigated in the literature using the stepwise two-photon excitation model. In this work, wehave appropriately considered the composite two-photon Rabi frequency approach for thisproblem. We have numerically solved the relevant density matrix equations for a three-levelatomic Yb system. Our values of optimal detunings are observed to be substantially differentfrom those reported in the literature.

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6. ULTRAFAST LASERS AND APPLICATIONS

6.1 Optical parametric amplifiers for generation of ultrafast laser radiations,P. Kumbhakar and K. Hussain, Dept. of Physics, National Institute of Technology, Durgapur,Durgapur-713209. Generation of ultrafast laser radiation is possible through simultaneous phase-matching and group-velocity matching in Ti:sapphire second harmonic pumped type-I opticalparametric amplifiers in several recently grown nonlinear optical crystals with judicious choiceof noncollinear geometry.

6.2 Focusing of femtosecond pulses in air – Multiple filamentation, P. Prem Kiran*,S. Bagchi and G. Ravindra Kumar, Tata Institute of Fundamental Research, 1 Homi BhabhaRoad, Colaba, Mumbai-400005. We present the onset of plasma filaments around the focalplane and evolution supercontinuum from tightly focused (f/6) 50 fs laser pulses (Ti:Sapphire,805 nm, 10 Hz) in air in the range of 10 – 85 above the threshold power for self-focusing (P

Cr)

for linear (LP) and circular (CP) polarized light pulses.

6.3 Characteristics of cross-polarized autocorrelation of ultrashort laser pulses,A.K.Sharma, P.A.Naik, and P.D.Gupta, Laser Plasma Division, Raja Ramanna Centre forAdvanced Technology, Indore 452013. In this paper, we present characteristics of cross-polarizedautocorrelation signals of 200fs laser pulses from cw mode locked Nd:glass oscillator usingcommercial LEDs as quadratic detectors. A modified Michelson interferometer was used torecord the AC signals with enhanced accuracy. The experimentally recorded AC signals werecompared with theoretically calculated AC signals.

6.4 Surface harmonic generation using femtosecond radiation with variable chirp,H.Singhal, P.A.Naik, V.Arora, U.Chakravarty, M.Raghuramaiah, R.A.Khan, S.R.Kumbhare,J.A.Chakera, P.D.Gupta and R. Ganeev#, Laser Plasma Division, Raja Rammana Centre forAdvanced Technology, Indore 452 013. #Akadempribor Scientific Association, Tashkent 700125,Uzbekistan. In this paper, we report the results of odd as well as even high harmonic generationup to the 15th order, ë = 52.9 nm, from different target surfaces. Chirp control of the drivinglaser radiation has been used for the tuning of the harmonic wavelength in the vacuum ultravioletrange. The harmonic frequencies were observed to shift with pulse chirp. Harmonics up to the12th order were tuned up to 3 nm.

6.5 Optimization of white light continuum in the spectral range 500 - 700 nm,J Jayabalan, A Singh, R.Chari and S M Oak, Ultrashort Studies Section, Raja Ramanna Centrefor Advanced Technology, Indore-452013. Optimization of femtosecond white light continuumgeneration in the 500-700 nm range from 100 fs, 800 nm pulses is reported. We show that it ispossible to get at low intensity a flat spectrum in specific spectral regions by optimizing thefocusing geometry and the medium length. Stringent control on the laser power stability and thelaser environment is required to get a stable and repeatable continuum.

NLS-6 68

6.6 Transformation of silver nanodiscs by laser photolysis, A Singh, J Jayabalan, P KMukhopadhyaya1, R.Chari, A. K. Nath1 and S M Oak, Ultrashort Studies Section 1 Solid StateLaser Division Raja Ramanna Centre for Advanced Technology, Indore-452013. In this paperwe report results of photolysis of silver nanodiscs in water. We have shown that the size andshape of silver nanodiscs can be modified in a controlled manner by exposure to pulsed lasersunder suitable conditions. Irradiation at high fluence causes the nanodisc to fragment. Howeverat low fluence values the nanoparticles start melting at the edges and the final size and shape isdecided by the laser intensity, exposure time and the host environment.

6.7 Study of the performance dependence of a regenerative amplifier on the seedpulse properties, K.C.Gupta, J.K.Fuloria, Paramita Deb, L.J.Dhareshwar, Rajasree V* andB.S.Narayan*, Laser & Neutron Physics Section, * Laser & Plasma Technology Division, BhabhaAtomic Research Centre, Mumbai-400 085. This paper reports the studies done on regenerativeamplifier setup for Chirped pulse amplification system. Performance of the regenerative amplifierwas studied with different seed pulse energy and pulse duration.

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7. NONLINEAR OPTICS

7.1 Third order optical nonlinearity of a Triarylmethane dye measured by Z-scantechnique, G.Vinitha, A.Ramalingam and P.K.Palanisamy, Department of Physics, AnnaUniversity, Chennai – 600 025. In this paper, the third order nonlinear optical properties ofMethyl violet 2B dye in ethanol and dye doped polymer film were measured by the Z-scantechnique. This material exhibits negative optical nonlinearity. The results show that Methylviolet 2B dye has potential applications in nonlinear optics.

7.2 A Comparative Study of Second Harmonic Generation in Indigenously GrownBBO Crystals of Different Compositions, A.K. Chaudhary 1, A.M. Rudra2 and U. Chatterjee1,1Department of Physics, Burdwan University, Burdwan-713104, 2Department of Physics, NetajiMahavidalya, Arambagh, Hoogly-712601. The paper reports the systematic study ofindigenously grown ( a) and (b) phase BBO crystals on the basis of their SHG efficienciesusing pulsed Nd:YAG laser. Ba++which is one of the principal ingredient of BBO crystalsmeasured by SEM-EDXA technique. The effect of the concentration of Ba ++ on generated SHsignals has also been correlated.

7.3 A novel technique of third harmonic generation of Nd:YAG laser in a single bulkBBO crystal, A. Saha, S. K. Das, A. Ray, M. Banik and P. K. Datta, Dept. of Physics & Met.,IIT-Kharagpur-721302. We report a novel technique for generating efficient third harmonic ofside diode array pumped, acousto-optically Q-switched Nd:YAG laser in a single crystal due tophase matched SHG and subsequent phase matched SFG process. This technique is as efficientas the technique of generation of THG using two NLO crystals.

7.4 Nonlinear absorption and refraction in solid films of Amido black dye under He-Ne laser light illumination, G.Sreekumar, B.Valsala Milka,, C.I. Muneera, Dept. Of Physics,University Of Kerala, Kariavattom ,Trivandrum K. Sathyamoorthy , C. Vijayan, Dept. OfPhysics,IIT Madras, Chennai. Saturable and reverse saturable absorption have been observedin solid films of Amido Black 10B at 632.8nm with He-Ne laser light, saturable absorptionswitching over to reverse saturable absorption as the concentration is increased.

7.5 Solitonic and Nearly Solitonic Beam Pairs, Punya P. Paltani and S. Medhekar,Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi-835215. Spatialsolitons have been extensively investigated because of their potential for all optical switchingand processing application. The self-guided propagation of spatial solitons of identical widthand different wavelength is possible, provided their intensities satisfy a certain condition. Notonly solitonic but nearly solitonic pairs are also important for all-optical devices. In this paperwe have identified the condition for two bright beams of different colour and even differentwidth so that they simultaneously propagate nearly undistorted in a homogeneous Kerr typefocusing medium.

NLS-6 70

7.6 Trapped breathers of two co-propagating beams in saturable nonlinear media,Ram Krishna Sarkar and S. Medhekar, Department of Applied Physics, Birla Institute ofTechnology, Mesra, Ranchi-835215. In this paper we have presented a theory on mutual-focusingof two coaxially co-propagating and mutually incoherent (i.e. both beams are fully spatially andtemporally coherent, but are incoherent with respect to one another) Gaussian beams in saturablenonlinear medium. We present formation of spatial breather pair (i.e. width of each beam oscillateswith the propagation distance) and show the existence line of spatially trapped breather pair(i.e. average width of each breather of the pair does not change with the propagation distance).

7.7 Nonlinear optical and optical limiting properties of phthalocyanines in solutionsand thin films of PMMA studied using cw excitation, S.J. Mathews, L. Giribabu,a and S.Venugopal Rao, Department of Physics, Indian Institute of Technology Guwahati, Guwahati781039, Assam, India a Nanomaterials Laboratory, Inorganic & Physical Chemistry Division,IICT, Hyderabad 500007. Phthalocyanines and their metal derivatives possess interestingnonlinear optical properties and find widespread applications in optical devices such as opticallimiters and all-optical switches. We present here some of our results on the nonlinear opticaland optical limiting studies of three different phthalocyanines in solution form and doped inPMMA film using low power cw excitation from a He-Ne laser at 633 nm.

7.8 Measurement of intensity dependent refractive index of fluorophosphate glass,A.P.Kulkarni, M.P.Kamath, A.S.Ioshi, M.N Kumbhare, P.D.Gupta, Laser Plasma Division, RajaRamanna Centre for Advanced Technology, Indore. R.Balkrishniah, C.K.Jayashankar,Department of Physics, Sri Venkateshwara University, Tirupati. We report measurement ofintensity dependent refractive index ( n

2 ) of a fluoro-phosphate glass containing strontium

oxide and small amount of KF. It is found that this glass has n2 value that is less than that of the

LHG-8 glass, the glass predominantly used in the amplifiers of high power lasers. This may beattributed to use of low atomic number cation Sr in the fluorophosphates glass mixture incomparison Ba used in the LHG-8 glass mixture.

7.9 Second harmonic conversion of large diameter Nd:Glass laser beam in quadrature,A.P.Kulkarni, M.P.Kamath, A.S.Joshi, P.K.Tripathi, Shashi Jain and P.D.Gupta, Laser PlasmaDivision, Raja Ramanna Center for Advanced Technology, Indore-452013. We report theconversion of laser radiation from one arm of Nd:phosphate glass high power laser (operationalin RRCAT, Indore) into it’s second harmonic using two type II potassium di-hydrogen phosphate(KDP) crystals in quadrature. A maximum conversion efficiency of 62 % was obtained at aninput laser intensity of 1.3 GW/ cm2. The conversion efficiency obtained by us matches wellwith the similar studies that are reported on NOVA laser.

NLS-6 71

7.10 Optical Phase Conjugation via Stimulated Brillouin Scattering in Dopedmagnetoactive Semiconductors, M. Singh, P. Aghamkar, S. Duhan, M. Sapra and N. Kishore,Department of Applied Physics, G. J. University of Sc. & Tech., Hisar-125001. Usingelectromagnetic treatment, optical phase conjugation via stimulated Brillouin scattering (OPC-SBS) in doped III-V piezoelectric semiconductors in presence of external magnetic field. Theorigin of Brillouin nonlinearity is taken into the process of electrostriction (g). To appreciate therole of piezoelectricity and magnetic field on OPC-SBS, a comparative study has been madebetween the piezoelectric and non-piezoelectric systems. We have shown that piezoelectricmagnetized semiconductors like n-InSb, n-GaAs can be a potential candidate materials for thefabrication of SBS based phase conjugate mirrors.

7.11 Third-order optical nonlinearity of carbon tetrachloride measured by z-scantechnique using Nd: YAG laser, M. Sapra, P. Aghamkar, M. Singh, S. Duhan and N. Kishore,Department of Applied Physics, G. J. University of Sc. & Tech., Hisar-125001. We report theexperimental measurement of nonlinear refractive index and absorption coefficient in twodifferent concentrations of carbon tetrachloride at 0.009mM and 0.01mM. The nonlinearrefractive indices of CCl

4 are found to be 1.23 X 10-9 cm2/MW, 1.18 X 10-9 cm2/MW and nonlinear

absorption coefficients are found to be - 0.6 X 10-10 cm/W,-0.8 X 10-10 cm/W for, 0.01mM and0.009mM respectively. The results indicate that with increasing the concentration of CCl

4 the

nonlinear refractive index increases, however absorption coefficient decreases.

7.12 Role of Biexcitonic Stark Effect on Nonlinear Absorption in NoncentrosymmetricQuantum dot, Swati Goyal 1 and Pranay K. Sen. Department of Applied Physics, Shri G. S.Institute of Technology and Science, Indore-452003; 1Department of Physics, Govt. AuotonomusHolkar Science College, Indore-452001. The nonlinear absorption is theoretically analyzed in aweak noncentrosymmetric CdTe quantum dot under strong confinement regime. We apply thetime dependent perturbation technique for a three level system to examine the biexcitonic andStark effect. The temporal and detuning behaviors of nonlinear absorption are analyzed withrespect to noncentrosymmetry; biexcitonic density; applied electric field and quantum dot size.An enhancement in the nonlinear optical absorption is achieved due to noncentrosymmetry,time dependent Stark shift and Stark broadening.

7.13 Fluorescence Detection and Collection Efficacy of a Fiber Optic Probe, ChitraChakravorty, Shubhada Kumbhaj and Pranay.K.Sen, Department of Applied Physics, ShriG.S.Institute of Technology & Science, Indore 452003. Design and development of a fiber opticprobe to estimate quantitatively the fluorescent spectroscopic outputs in terms of the collectionefficiency as a function of the target to probe distance. The probe developed in the laboratoryhas been tested for Rhodamine 6G dye both in absence and presence of polystyrene as a scatterer.

NLS-6 72

7.14 Measurement of nonlinear refraction of various solvents under femtosecond pulseexcitation, C.P.Singh, K.S.Bindra and S.M.Oak, Ultrafast Studies Section, Raja Ramanna Centrefor Advanced Technology, Indore-452 013. We have measured nonlinear refraction (n

2) of various

solvents with the Z-scan technique using Ti:Sapphire laser with 100 femtosecond pulses at 800nm. We found that in the femtosecond pulse excitation regime the n

2 values are about one order

of magnitude smaller than the picosecond pulse excitation regime. This is due to the fact that forpicosecond pulses both mechanisms bound electronic and molecular reorientation Kerr effectcontribute whereas for femtosecond pulses only bound electronic nonlinearity contributes tototal signal.

7.15 Second harmonic generation in P-Nitro Aniline, M. Das, R. Trivedi, P. Sen, R. Prasad1

and P. K. Sen, Department of Applied Physics, S G S Institute of Technology & Science, Indore-452 003, 1School of Chemical Sciences, D.A.V.V., Takshila Campus, Indore-452017. In the presentpaper, we have reported the experimental as well as theoretical study of the first-orderhyperpolarizability (â) of dimer of p-NA and have compared the results with those of urea, astandard organic material. The theoretical results are in good agreement with experimentalobservations.

7.16 Investigation of spectral and nonlinear optical properties of azo dyes, C.Gayathriand A. Ramalingam, Department of Physics, Centre for Laser Technology, AnnaUniversity,Chennai 600 025. The relative contributions from nonlinear absorption (NLA) andnonlinear refraction (NLR) has been measured using a diode-pumped Nd: YAG laser at 532nm.Experimental results show that all the investigated organic dye molecules exhibit saturationabsorption and negative nonlinearity. The | ÷(3)| is of the order of 10-6 esu.

7.17 SIT Bragg soliton pulse compression in a doped non-uniform fiber Bragg grating,P. Ramesh BabuA, K. SenthilnathanB, K.PorsezianC and V. SanthanamD, ADepartment of Physics,Vellore Institute of Technology, Deemed University, Vellore, BDepartment of Electronic andInformation Engineering, Hong Kong Polytechnic University, Hung Hom Kowloon, Hong Kong,CDepartment of Physics, Pondicherry University, Pondicherry ,DDepartment of Physics,Presidency College, Chennai. We investigate the Bragg soliton pulse compression in a onedimensional non-uniform nonlinear periodic structure doped uniformly with the inhomogeneouslybroadening two-level atoms. The Bragg solitary pulse compression is analyzed with appropriategrating induced dispersions.

7.18 Pump focal geometry for high average power bbbbb-BaB2O4 optical parametricoscillator, R. C. Bapna, C. S. Rao and K. Dasgupta, Laser and Plasma Technology Division,Bhabha Atomic Research Centre, Mumbai-400 085.

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8. LASER SPECTROSCOPY

8.1 Anisotropy Shift study in carbonyl containing molecule Methyl Isobutyl Ketone,Th. Gomti Devi a, Soma Datta b and K.Kumarb, a Department of Physics, NERIST, Nirjuli-791109 Arunachal Pradesh b Department of Physics, North- Eastern Hill University, Shillong-793022, Meghalaya. The anisotropy shift of the C=O containing molecule Methyl IsobutylKetone has been studied in various solvents. The continuum model of Onsager-Fröhlich is notfound to be valid for most of the systems. The repulsive potential of the type e-aR plays animportant role in the interactions of complex molecules.

8.2 Laser Raman and Infrared Spectra, electronic structure calculations andAssignments for 5, 6-Benzo- and 7, 8-Benzo-4-Azidomethylcoumarins, Anuradha Ramojia,Jayashree Yenagia, J.Tonannavara, R. Kusanurb and M.V. Kulkarnib.aDept.of Physics, bDept. ofChemistry, K.U.Dharwad. Laser Raman and Infrared spectral measurements have been carriedout for the laboratory prepared, solid 5, 6-benzo- and 7, 8-benzo-4-azidomethylcoumarin (I andII respectively). Restricted Hartree-Fock (RHF) and DFT’s B3LYP levels combined with standardGaussian basis sets, 6-31G*, have been used in the calculations, giving electronic energies,optimized structures and theoretical spectra.

8.3 Fourier Transform Laser Raman and Infrared spectra, ab initio/DFT and normalcoordinate analysis of 2-Chloro-3,6-difloro-,3-Chloro-2,6-difloro-and 2-Chloro-6-fluoro-3-methylbenzaldehydes, C.S.Hiremath, Department of Physics, P.C.Jabin Science College,Hubli, S.B.Doddamani , Jayashree.Yenagi and J. Tonannavar, Department of Physics, KarnatakUniversity, Dharwad. Experimental Raman and infrared spectra were recorded for solid samples.RHF/ 6-311G, B3LYP/6-311G and normal coordinate calculations have been performed. Acomplete assignment of the observe spectra on the basis of spectral correlations, electronicstructure calculations and normal coordinate calculations have been proposed.

8.4 Design and Characterization of a QUIC Trap, S. R. Mishra1, S. P. Ram1, P. P.Dwivedi2, S. K. Tiwari1 and S. C. Mehendale1, 1Laser Physics Applications Section, RRCAT,Indore-452 013, 2School of Physics, Devi Ahilya Vishwavidyalaya, Indore-452 017. A QuadrupoleIoffe configuration (QUIC) trap for trapping of Rb87 neutral atoms has been designed, fabricatedand characterized. Based on simulations of magnetic field for two quadrupole coils and oneIoffe coil, the trap parameters were fixed. The coils were fabricated and encapsulated in jacketsto provide cooling with flowing water. We observed the formation of required Ioffe configurationin this trap for currents of 23 A in quadrupole coils and 29 A in Ioffe coil.

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8.5 Matrix effect on the sensitivity of Laser-induced breakdown spectroscopy, ShiwaniPandhija and A. K. Rai, Laser spectroscopy research laboratory, Department of Physics,Allahabad University, Allahabad. The present study is planned to analyze the toxic elementspresent in industrial area by using Laser-induced breakdown spectroscopy (LIBS). In the presentpaper, the temperature of plasma is evaluated by using atomic lines of Pb emitted in the Laser-induced plasma of Pb(NO

3)

2. The plasma temperature evaluated in soil matrix containing Pb is

different from the that of Pb(NO3)

2 sample at same experimental conditions. Thus our results

clearly demonstrate that the plasma temperature is dependent of thermal properties of material.We have also calculated the detection limit for Pb in soil, which is of the order of 40 ppm.

8.6 Detection of Chromium in liquid with Laser-induced Breakdown Spectroscopy,Nilesh K. Rai and A. K. Rai, Laser Spectroscopy Research Laboratory, Department of Physics,University of Allahabad, Allahabad. Water pollution is a worldwide problem that may lead todisease related to liver, skin disease etc. The monitoring pollutants in water by an accurate andsensitive technique have always been a challenge. Laser-induced Breakdown Spectroscopy(LIBS) is suitable for spectrochemical analysis of liquids. This technique has potential merit torapid, real time, and online measurement of elements present in trace amount in sample. Inpresent paper, we will describe the result of the fabrication of liquid jet having nozzle diameter< 1mm for the detection of Cr in water. Using this experimental setup a detection limit of Cr is21ppm.

8.7 Emission of Rhodamine 6 G dye in a stationary solution, Nidhi Sharma, NageshwarSingh*, Sneh Lata Goyal and H S Vora*, Department of Applied Physics, Guru JambheshwarUniversity, Hisar- 125001, *Raja Ramanna Centre for Advanced Technology, Indore – 452013..In this paper, we report the observations on the fluorescence of Rhodamine 6G dye in ethyleneglycol solvent in stationary solution transversely pumped by a high repetition rate copper vaporlaser (CVL). The fluorescence FWHM of Rhodamine 6 G increases with temperature of themedium and peak emission wavelength also show slight shift and fluctuations. This is an importantissue, which should be taken into consideration for the development of stable narrow bandwidthdye laser.

8.8 Importance of the Persistent Band heads of Nitrogen in the LIF of MeteoriteSample, R. Changmai and G.D. Baruah Department of Physics, Dibrugarh University-786004.Laser induced fluorescence spectra of a number of samples in thin solid films of polymers;moluscan shells and a meteorite sample have been exited with the help of a Ar+ laser. Thepersistent band heads of nitrogen at 5407.1 Å (11,6) and 5372.8 Å (12,7) have been observed inthe LIF of all the samples. One of the salient points of observation is that these persistent pair oflines have also been observed in the LIF of a meteorite sample leading to speculation that theparticular sample of meteorite contains nitrogen which is indicative of amino acid. The meteoritesample, unless contaminated by terrestrial compounds to large extent, may throw light on theevolution of life through these persistent lines. The persistent lines of nitrogen first positivebands are never quenched under any circumstances. The present work analyses the extractionof spectroscopic information on a solid film via use of the persistent lines of molecular nitrogen.

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8.9 Laser Spectroscopy of Fabricated Rh B Doped Polymer Optical Fiber, NitishKumar, Saurabh Raj, VPN Nampoori and C P Girijavallabhan; Centre of Excellence in Lasersand Opto-electronic Sciences, CUSAT, Kerala. Laser dyes are highly efficient media either forlaser source with narrow pulse width and wide tunable range or for optical amplifier with highgain, high power conversion and broad spectral bandwidth. Rhodamine B doped POF wasfabricated and the fluorescence characteristics of the fiber were carried out using 532nm radiationfrom a DPSS laser. The fluorescence spectra at varying propagation length through the fiberwere studied. Spectral peak shows red shift as propagation distance is increased. Results alsoshow the spectral line narrowing as a function of pump power.

8.10 Raman anisotropic bandwidth dependence on van der Waals’ volume of thecomplex interacting systems, Soma Datta b,Th. Gomti Devi a and K.Kumar ba Department ofPhysics, North- Eastern Hill University, Shillong-793022, MeghalayabDepartment of Physics,NERIST, Nirjuli-791109, Arunachal Pradesh. Raman band shape analysis for anisotropic Ramancomponent was carried out for the C=O stretching mode of Acetophenone using various polarand non-polar solvents as a function of the solvents’ hydrodynamic properties. In order to interpretthe solute-solvent behaviour we have taken into account the van der Waals’ volume (V

w) of the

sphere of influence for solute dissolved in solvents. It has been observed that the repulsivepotential of the type e-aR plays an important role in the interactions of complex molecules.

8.11 Effect of Drying Time on Absorption Properties of Coumarin-120 in Sol-Gel MatrixAparna V. Deshpande and Jayraj R. Rane, Physics Department, Univers.ity Institute of ChemicalTechnology, Matunga, Nathalal Parikh Marg, Mumbai-400 019. Preparation of coumarin-120(C-120) sol-gel glass samples with HCl as catalyst using Sol-gel method has been reported. Theeffect of drying time on spectroscopic properties of C-120 in sol-gel glass is reported by comparingthese with C-120 in methanol (MeOH).

8.12 FT-Raman spectroscopic analysis of Archaeological potteries excavated atMaligaimedu, Cuddalore District in Tamilnadu, India, R.Palanivel*, G.Velraj, K.Janaki andA.Mohamed Musthafa, *Department of Physics, Annamalai University, Annamalainagar-608002.Department of Physics, Periyar University, Salem-636011. FT-Raman spectra were recordedusing Nd: YAG laser excited at 1064 cm-1 for some of the Archaeological pottery shreds collectedfrom Malligaimedu, which is one of the archaeological site in Tamilnadu. An attempt has beenmade to identify the clay minerals present in the pottery specimens from the tentative assignmentsof the Raman shifts observed from the spectra in the range from 3500-250cm-1.

8.13 Surface enhanced raman spectral investigations of 1,5-DipiperidinoAnthraquinone on silver nanosol under laser excitation, M.Umadevi and V.Ramakrishnan1,Department of Physics, Mother Teresa Women’s University, Kodaikanal, 1 Department of LaserStudies, Madurai Kamaraj University, Madurai. Surface enhanced Raman spectra of 1,5–dipiperidino anthraquinone (1,5-DPAQ) have been examined to elucidate the orientation of1,5-DPAQ on silver nanosol. The vibrational features observed in SERS suggest that themolecules are chemisorbed. The adsorption of the molecule is through p electrons in theanthraquinone ring and the axial lone pair of electrons of nitrogen. The orientation of the moleculeis found to be ‘flat–on’.

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8.14 Flavine Adenine Dinucleotide (FAD) dynamics in water by measuring fluorescenceand photoacoustic signals simultaneously, Sudha D. Kamath and K.K.Mahato. Centre forLaser Spectroscopy , MAHE, Manipal. We have analysed the fluorescence and photoacousticspectra recorded simultaneously at different concentrations of FAD showing how the radiativeand non-radiative relaxation pathways differ as a function of concentration. Fluorescence andphotoacoustic measurements were carried out using 325 nm excitation. For fluorescencerecording, spectrograph ICCD combination is used and for PAS recording, PZT transducercoupled to a homemade PA cell with Transient digitizer combination is used.

8.15 Natural Bond Orbital analysis and SERS spectral investigations of L-HistidiniumDihydrogenmonophosphate Monohydrate, V. Beena Jothya+, T. Vijayakumara, V.S. Jayakumara

and I. Hubert Joea, aCenter of Molecular and Biophysics research, Department of Physics,Mar Ivanios College, Tiruvananthapuram - 629 015, Kerala. +Department of Physics, Women’sChristian College, Nagercoil - 629 001, Tamil Nadu. Hydrogen bonded L-HistidiniumDihydrogenmonophosphate Monohydrate (LHDM) crystals are grown are grown at roomtemperature by the slow evaporation technique. The hydrogen bonding geometries using NBOanalysis indicate the presence of C-H—O, N-H—O and O-H—O bonds. SERS spectralinvestigations show that the molecule is adsorbed to the silver surface via oxygen atoms of theorthophosphoric acid group which indicates the nearness of the orthophosphoric molecule tothe Ag surface.

8.16 Effect of size and shape anisotropy on hole energy states in CdSe quantum dots,J. Kumar S. Kapoor, S. K. Gupta, and P. K. Sen, Department of Applied Physics, Shri G SInstitute of Technology & Science, Indore-452 003. In this paper we have studied the effect ofsize and shape anisotropy on the hole energy states of the CdSe quantum dots theoretically. Thequantum dot is modeled using anisotropic parabolic confinement potential. The complex structureof the valence band is described by Luttinger Hamiltonian. The energy spectra and eigen functionsof hole states are calculated by numerical diagonalization of the Hamiltonian. The results showsignificant effect of anisotropy and valence subband mixing on the hole energy spectra.

8.17 Magneto-absorption studies of strained CdSe/ZnSe quantum dots, S. K. Gupta, J.Kumar, S. Kapoor and P. K. Sen, Department of Applied Physics, Shri G S Institute of Technology& Science, Indore-452 003. This paper is devoted to the theoretical analyses of absorptionspectra of strained CdSe quantum dots under the influence of an externally applied magneticfield. The confinement potential is considered to be that of a finite well along the growth direction,while the in-plane confinement is taken to be parabolic. The magnetic field effects and thevalence band fine structure is incorporated using Luttinger Hamiltonian. The results show thatstrain effects dominate magnetic field induced effects. The spin-splitting due to application ofmagnetic field is observed only at high magnetic field strengths.

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8.18 Selective Photochemical Reaction of 32SF6 with H 2S on Irradiation with a TEACO

2 Laser, L. Abhinandan, N .S. Benerji, N. Varshnay, U. Nundy and P .N. Bajaj* RRCAT,

Indore, *BARC, Mumbai. In this paper we describe the results of selective photochemical reactionof 32SF

6 on irradiation with a TEA CO

2 laser. It has been observed that SF

6, in a vacuum-baked

reaction cell, undergoes reaction with H2S as reactant at laser fluence and intensity that are

much lower than the reported values for multi-photon dissociation of SF6. The reaction is also

found to be isotopically selective.

8.19 On the origin of dual band emission from UV exposed TPD solution, M.P. Joshi1,S. Raj Mohan1, Beena Jain2, T. S. Dhami1 and S. K. Tiwari1, 1Laser Physics Application Section,2Biomedical Application Section Raja Ramanna Centre for Advanced Technology, Indore-452013. The origin of dual band blue-green photoluminescence (PL) from UV exposed TPDsolution is investigated using solvent and excitation wavelength dependence PL and PL lifetimes.Emission in blue region is due to locally excited transitions of TPD and other byproducts.While emission in green seems to arise due to exciplex formed amongst photoproducts of TPD.

8.20 FTIR and Raman scattering studies of 3-Formylphenylboronic acid using DensityFunctional Theory, C.James �, C. Ravikumar , V.S.Jayakumar and I.Hubert Joe, Centre forMolecular and Biophysics Research, Department of Physics, Mar Ivanios College,Thiruvananthapuram – 695 015, Kerala.� Permanent address: Department of Physics, ScottChristian College, Nagercoil –629 003, Tamilnadu. NIR-FT Raman and FT-IR spectra of thecrystallized 3-Formylphenylboronic acid (C

7H

7BO

3) have been recorded in the region 4000-400

cm-1. The spectral interpretation has been done following full structure optimization andfrequency calculations based on the ab initio Density Functional Theory using the standard 6-31G* basis set. The predicted vibrational spectra are in fair agreement with experiment. Theoptimized geometry favors near planarity of the molecule other than a slight twist around C—Bbond of boronic acid. The delocalization of unpaired electron of oxygen atom onto the ring psystem causes unusual downshift of C=O stretching frequency. The red shift in OH stretchingfrequencies reveals the existence of strong intermolecular O-H…O hydrogen bonding.

8.21 FT-IR and FT-Raman spectral investigation and Quantum Chemical computationsof Melaminium chloride hemihydrate, S. Joona, C.James †, C.Ravikumar, V.S.Jayakumarand I.Hubert Joe, Centre for Molecular and Biophysics Research, Department of Physics, MarIvanios College, Thiruvananthapuram – 695 015. † Department of Physics, Scott ChristianCollege, Nagercoil –629 003, Tamilnadu. The single crystals of Melaminium chloridehemihydrate were grown by slow evaporation technique and vibrational spectral analysis wascarried out using NIR-FT Raman and FT- IR spectra. The ab initio quantum chemicalcomputations were also performed at HF/6-31G(d) level to derive the optimized geometry,vibrational frequencies and first hyperpolarizability of Melaminium chloride hemihydratemolecule. Vibrational spectral analysis indicates the presence of N-H—O and N-H—Clintermolecular hydrogen bonding.

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8.22 Vibrational spectroscopic study of Anisaldehyde and 4-Hydroxyacetophenone indifferent binary mixtures, A.Anis Fathimaa, K.Prema Lathaa, M. Umadevib andV.Ramakrishnana, b Department of Physics, Mother Teresa Women’s University, Kodaikanal –624 102, aDepartment of Laser Studies, School of Physics, Madurai Kamaraj University,Madurai–625 021. Spectroscopic study of neat anisaldehyde (4MeOBz), solvated ions 4-Hydroxyacetophenone and their binary mixtures with varying mole fraction of 4MeOBz, 4-Hydroxyacetophenone were investigated. The concentration dependence of wave number positionand line width (FWHM) was analyzed to study about the interaction of solute vibrational modewith the microscopic solvent environment.

8.23 Solvation of Alizarin in binarymixtures, V.Sasirekha, M.Umadevia andV.Ramakrishnan, Department of Laser Studies, School of Physics, Madurai Kamaraj University,Madurai–21,. aDepartment of Physics, Mother Teresa Women’s University, Kodaikanal – 02.Preferential solvation of a Alizarin(AZ) has been studied in a non protic and a protic solventsand its binarymixtures.Solvatochromic shifts of the ground and excited states of the AZ wereanalysed by monitoring the charge transfer absorption band and the fluorescence emission spectrain terms of the solute–solvent and solvent-solvent interactions. It provides an indication of themicroenvironment immediately surrounding the probe.

8.24 Observation of auto-ionization resonances of Sm from a filament based atomic-beam source, A.K. Pulhani, M. L. Shah, Vas Dev and B. M. Suri, Laser & Plasma TechnologyDivision, Bhabha Atomic Research Center, Mumbai. We report the development of filamenttype atomic beam source of Sm and also observation of new odd-parity auto-ionization resonancesof Sm using three-color three-photon photoionization experiments. This work can be extendedfurther to perform resonance ionization spectroscopy of lanthanides, actinides, and trans-actinides,which had been a challenge for the experimentalist, particularly when they are only available intrace amounts or are radiotoxic.

8.25 Measurement of Branching Ratios and Transition Probabilities in AtomicSamarium using Laser - Induced Fluorescence, M. L. Shah, A. K. Pulhani Vas Dev, G.P.Gupta and B. M. Suri, Laser and Plasma Technology Division, Bhabha Atomic ResearchCentre, Mumbai – 400085. Branching ratios of several transitions of Sm were determinedfrom the excited upper levels using laser-induced fluorescence (LIF) technique. Using thesemeasured values of the BR

ki and the reported lifetimes of the excited upper levels (measured

using a time-resolved LIF technique), we have determined the values of transition probabilities(A

ki ). The results from this work are found to be in good agreement with the previously measured

values.

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8.26 Molecular Nonlinear Optical Responses and Vibrational Spectra of Ethyl 3-(3, 4-dihydroxy phenyl) -2-propenoate, D.Sajan, Chun-Nian Xia1 Wei-Xiao Hu1, I. Hubert Joe andV.S.Jayakumar, Centre for Molecular and Biophysics Research, Department of Physics, MarIvanios College, Thiruvananthapuram-695 015. 1College of Pharmaceutical Science, ZhejiangUniversity of Technology, Hangzhou, China. The NIR-FT Raman and FT-IR spectral analysisof potential NLO material Ethyl 3-(3, 4-dihydroxyphenyl)-2-propenoate (EDHP) is carried outby density functional computations. The SHG efficiency is tested using Q- switched Nd: YAGlaser of wavelength ë at 1064nm, which is approximately 2.5 times that of urea. Optimizedgeometry reveals that the increase of the angles C

6-C

1-C

2 and C

4-C

5-C

6 by 2.1° and 1.2°

respectively and reduction in endocyclic angle C6-C

1-C

2 by 2.5°, associated with the charge

transfer interaction. The simultaneous infrared and Raman activation of C7 = C

8 stretching and

phenyl ring modes clearly points to the charge transfer interaction between C=O group andphenyl ring through the ethylenic bridge. The ð- electron cloud movement from donor to acceptorcan make the molecule highly polarized and the intra molecular charge transfer interaction mustbe responsible for the NLO properties of EDHP.

8.27 Poly Phosphazene with Pendant Oil Red O - A Nonlinear Optical Polymer forElectro-Optic Applications, T.Vijayakumar1, I. Hubert Joe1, T. Shrisudha2, Dona Mathew2

C.P Reghunadhan Nair2 and V.S. Jayakumar1, 1Dept. of Physics, Mar Ivanios College,

Thiruvananthapuram-695015, 2Polymers and Special Chemicals Division, Vikram SarabhaiSpace Centre, Thiruvananthapuram-695022. A comprehensive investigation of thepolyphosphazene NLO polymers with pendant ORO and DR1 has been carried out to determinetheir linear and non-linear optical properties. These molecular systems show large non-linearoptical activity. The dipole moments (m), polarizabilities (a), static hyperpolarizabilities (b

tot)

and the frontier molecular orbital energies are calculated. The inverse relationship of HOMO–LUMO gap with the total static hyperpolarizability is analysed based on computed results. Thestructural features responsible for the very large non-linear optical activity in these polymericsystems have also been discussed.

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9. LASER PLASMA INTERACTION

9.1 High voltage pulse generators for laser plasma experiments, Jankee Upadhyay andC.P.Navathe, Laser Plasma Division, RRCAT, Indore-452013. This paper describes the differenttopologies for generation of high voltage pulse for pulsed plasma experiments. The first schemeuses two switches for generating fast rise and fall times and the second scheme uses a self-matched transmission line. In the scheme based on self-matched transmission line, onwe haveachieved a flat top pulse with continuously variable amplitude from 800 V to 3.8 kV by varyingthe load impedance and variable pulse duration from 5 ns to 38 ns by varying the delay intriggering of the two switches.

9.2 Relativistic Self-guidance in magnetized Plasmas, Meenu V Asthana, Amit Goswamiand S. Sharma, Department of Physics, M.B. Khalsa College, Indore. Intense magnetic fields~100 MG arise from the push given to the background electrons by the relativistic ponderomotiveforce during interaction of a very short and intense laser pulses in plasmas. We establish creationof a plasma channel by a self-guided, high intensity (>1018 W/cm2), short laser pulse as itpropagates in an under dense plasma.

9.3 A Model for the Interaction of Intense Short Laser Pulses with Atomic Clusters,A. R. Holkundkar and N. K. Gupta, Laser & Neutron Physics Section, Bhabha AtomicResearch Centre, Mumbai –400 085. A model for the interaction of intense lasers with atomicclusters is presented. The model takes in to account the spatial non-uniformities of a cluster asit evolves in time. The cluster is treated as a stratified sphere having arbitrary number of layers.Electric and magnetic fields are obtained by solving the Helmholtz equation. All components ofelectric and magnetic fields (incident and scattered) are expanded in vector spherical harmonicfunctions. Expansion coefficients are obtained using sufficient number of necessary boundaryconditions at layer interfaces by a recursive algorithm. Scattering and absorption cross sectionsare obtained from the knowledge of expansion coefficients. Results are compared with publishedresults.

9.4 Spot size evolution in axially magnetized plasma, Rohit K. Mishra, Ajay K. Upadhyay,Gaurav Raj and Pallavi Jha, Department of Physics, University of Lucknow, Lucknow 226007.Inthis paper propagation of intense, circularly polarized laser pulse in axially magnetized plasmais analyzed. Nonlinear wave equation is set up and source dependent expansion (SDE) methodis used to obtain the evolution of laser spot. The effect of magnetic field on self-focusing propertyof laser pulse is studied and the critical power for self-focusing is obtained.

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9.5 Envelope evolution and modulation instability of a laser beam in partially strippedplasma, Gaurav Raj, Ajay K. Upadhyaya, Rohit K. Mishra and Pallavi Jha, Department ofPhysics, University of Lucknow, Lucknow-226007. In the present paper we study the combinedeffect of relativistic and ponderomotive nonlinearities on the propagation characteristics andatomic modulation instability (AMI) of a laser beam propagating through partially strippedplasma. For studying envelope evolution and AMI, the contribution of coupling betweenfundamental and harmonic electromagnetic modes to the nonlinear polarization field and currentdensity has been considered.

9.6 Analytical Study of HChG-Laser Beam Propagation in Collisional Plasma, M. V.Takale, S.T. Navare, S.D. Patil and M.K. Soudagar, Department of Physics Shivaji University,Kolhapur-416 004. We have studied the propagation of m=0,1 and 2 mode HChG- laser beamsin collisional plasma. The field distribution in the medium is expressed in terms of beam-width(f) and decentered (b) parameters. The differential equations for f parameter are established byparabolic wave equation approach under paraxial ray approximation. Analytical solutions areobtained for the condition Rn < Rd. The behaviour of f parameter with propagation distance forvarious b values is examined by numerical estimates. The results are presented graphically. It isobserved that m = 0 beam is self-focused for all b values while m=1 and m = 2 beams arediverged for b= 0 and b = 1 values. For a given mode, the beam gets self focused at shorterdistances for higher b values.

9.7 Propagation of short laser pulses in a plasma channel, Ajay K. Upadhyay, Gauravraj, Rohit K. Mishra and Pallavi Jha, Department of Physics, University of Lucknow, Lucknow-226007. In this paper propagation of a linearly polarized laser pulse in a parabolic plasmachannel is described with the helpof the Lagrangian density of the wave equation, evolution oflaser spot and pulse length are analyzed.

9.8 High order harmonic generation from plasma plumes : Tuning of the harmonicwavelengths by varying the chirp of the laser pulse, H. Singhal, P. A. Naik, U. Chakravarty,V. Arora, J. A. Chakera, R. A. Khan, M. Raghuramaiah, S. R. Kumbhare, P. D. Gupta and R.Ganeev#, Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore452013. #Akadempribar Scientific Association, Tashkent 700125, Uzbekistan. In this paper, wepresent a study of high order harmonic generation from laser produced plasma plumes. Harmonicsup to 61st order have been recorded. It is shown that the frequency of the harmonics can bevaried by varying the chirp of the laser pulse, which gives a handle to tune the harmonic frequency.

9.9 Hard x-ray spectroscopy of femtosecond laser produced plasma, V.Arora, H.Singhal,P.A.Naik, U.Chakravarty, R.A.Khan, J.A.Chakera, and P.D.Gupta, Laser Plasma Division,Raja Rammana Centre for Advanced Technology, Indore-452 013. We report aon the developmentof a NaI (Tl) scintillator based hard x-ray spectrometer and its use for recording hard x-rayspectrum from plasma produced by 50 fs Ti:Sa laser focused at an intensity of ~ 1018 Wcm-2.Hard x-ray emission spectrum from the copper plasma was recorded in 150 keV – 1.5 MeVrange. Hot electron temperature of 469 ± 56 keV was deduced from this spectrum.

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9.10 X-ray CCD camera based crystal spectrograph for x-ray spectroscopy of laserproduced plasmas, V.Arora, H.Singhal, P.A.Naik, U.Chakravarty, R.A.Khan, J.A.Chakera,R.Jain, H.S.Vora, and P.D.Gupta, Laser Plasma Division, Raja Rammana Centre for AdvancedTechnology, Indore-452 013. A high-resolution x-ray crystal spectrograph with x-ray CCD asdetector has been set up for on-line measurements and analysis of x-ray emission from laserproduced plasmas. Its operation in the spectral range of 8.5 – 9.5 Å has been demonstrated witha spectral resolution of 16m Å. Its spectral range can be changed by suitable movement of thecrystal placed on a motorized translation stage. Details of this spectrograph are presented.

9.11 Ion emission from nanostructured surfaces, S.Bagchi, P. Prem Kiran, M.K. Bhuyan,S. Bose, P. Ayyub, M. Krishnamurthy and G. Ravindra Kumar, Tata Institute of FundamentalResearch, 1 Homi Bhabha Road, Colaba, Mumbai-400005. We present results on the emissionof ions from ultraintense fs laser produced plasma from ellipsoidal copper nanoparticles coatedon polished Cu. The role of surface roughness on the particle beam divergence will be presentedas a function of incident laser energy.

9.12 Enhanced electron yield and absorption in laser interaction with doped clusters,R.Rajeev, J.Jha and M.Krishnamurthy, Tata Insitute of Fundamental Research,1,Homi BhabhaRoad,Colaba, Mumbai 400005. The electron energy distribution from nano-cluster plasmasthat are formed when CH

3I doped Ar clusters are irradiated by intense ,100 fs laser pulses of

intensity ~ 1014 W/cm2 were measured. Enhanced electron yields were observed in the case ofdoped clusters under same experimental conditions. Absorption measurements indicated thatlaser energy is efficiently absorbed by doped clusters than pure clusters at the same stagnationpressure.

9.13 Dynamics of expanding Li plasma produced by laser blow off of LIF-C multilayertarget, R.K. Singh1, Ajai Kumar1 and K.P. Subramanian2, 1Institute for Plasma Research, Bhat,Gandhinagar, 2Physical Research Laboratory, Navarangpura, Ahmedabad. We have used timeand space resolved optical emission spectroscopy to study the expansion dynamics of Li plasmagenerated by laser blow off (LBO) of a multilayer LIF-C film. The evolution features of Li*(670.8 nm) and Li+* (478.8 nm) were studied in different ambient environment (argon pressureranging from high vacuum to 3 mbar) and at various laser fluence. It has been found that somestriking difference between the expansion behavior of neutral and ionic Li atom with regard toplume splitting, confinement and tharmalisation of species. The result show that, there is athreshold distance from the target (Z=4 mm) above which the expansion dynamics changesfrom free expansion to a collisional regime. Comparative analyses of experimental results alsoindicate that many feature of LBO plume resemble the conventional laser produced plasma.

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9.14 Ion emission from laser plasmas generated from metallic nano-particle coatedtargets, S.Chaurasia ,Diwakar S.Munda,C.G.Murali, Rajashree.V2,A.C.Shikalgar2,B.S.Narayan2, N.K.Gupta, Pushan Ayub 3 and L.J.Dhareshwar . Laser & Neutron Physics Section,Physics Group. 2Laser & Plasma Technology Division, Bhabha Atomic Research Centre,Mumbai-400085.

3Department of Condensed Matter Physics, Tata Institute of Fundamental

Research, Mumbai-400005. Interaction of intense lasers with nano-particles and clusters hasbecome a subject of intensive study in the recent times. Significant enhancement in soft andhard X-ray emission has been reported by several authors in targets with structured surfaces1,2.Significant enhancement in laser light coupling in plasmas created from copper nano-particletargets using 100fsec laser pulse at 806nm has been reported3. Laser absorption processesinvolved in the laser-plasma interaction have an effect on the ion emission characteristics also.In our experiments reported here, we have studied the ion emissions from plasmas producedfrom solid polished copper targets having a 1µm thick layer of copper nano-crystalline particlesof about 50nm size. The laser used in these experiments has a commercial Nd:glass laser oscillatorhaving a continuously variable pulse duration from 300 to 800psecs. . The energy output fromthe oscillator is about 100mJ. The maximum laser energy of about 2Joules and the focusedintensity on targets was in the range 1013to 1014W/cm2. It is observed that the behaviour ofplasma generated from copper nano-particle coated target is different from that of plain coppertarget. It is observed that the ion flux in case of nano-particle coated copper targets is higher forP polarization of the laser pulse as compared to S polarization. Also, nano-particle coated targetsshow higher flux compared to plain copper. The same is observed for ion velocity also. Sinceion flux is dependant on mass ablated which in turn depends upon the laser energy absorbed, wecan conclude that the laser energy absorption is higher in nano-particle coated targets as comparedto plain targets for P polarized light.

9.15 Formation of supershort electron beam and volume discharge in gases underatmospheric pressure, V.F. Tarasenko, Institute of High Current Electronics, SB RAS,Akademichesky Ave., 2/3, Tomsk, 634055, Russia. An electron beam and volume dischargewith formation conditions in gases under atmospheric pressure in a gap with a cathode having asmall curvature radius have been investigated. The properties of runaway electrons and X-rayradiation produced using a nanosecond volume discharge are examined.

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10. LASERS IN INDUSTRY AND DEFENCE

10.1 Laser seeker system, A.P.Revathy and GNVS Kasi V Rao, MST Div, ADE, DRDO,Bangalore-93. Laser Seekers operating in the semi-active mode is used for the guidance andimproved accuracy of weapon hitting the targets. Acquisition of the reflected laser pulses fromtargets at different stand off distances were tested using seeker system with 200 Field of viewand silicon quadrant detectors and preamplifier operating in trans-impedance amplifier mode.The amplified pulses were stretched from 12 ns to 100ms using pulse stretchers in two stages.The four output signals were checked experimentally with the laser power measured using theprobes. The four outputs were balanced using linearization methods.

10.2 Real-Time Holographic Interferometry for Industrial Applications, K. Bose, J. T.Andrews and P. K. Barhai, Dept. of Appl. Physics, BIT, Mesra, Ranchi. Digital real-timeholographic interferometry is developed to diagnose metallic and non-metallic samples fordefects. This technique allows measurement and testing of both uniform and non-uniform surfacesand has immense potential for immediate adaptation to Industry where the sample is required tobe monitored regularly for different environmental conditions. The technique is currently extendedto various other measurements for verification of the setup as well to diagnose samples.Development of prototype of the setup is under progress for application in industrial environment.

10.3 Finite Element Analysis of Residual Stress and Distortion in Laser Welded Plate,M. Sundar, A.K. Nath1, D.K. Bandyopadhyay, S.P. Chaudhuri, D. Misra and P.K. Dey, School ofLaser Science & Engineering, USIC Building, Jadavpur University, Kolkata-700032, 1Head,ICL, RRCAT, Indore. Localized heating during welding followed by rapid cooling generatesresidual stress & distortion. One of the main problems faced during welding is the selection ofthe appropriate combination of input variables for achieving minimum residual stress anddistortion. In the present work a study on a single pass butt-welding specimen by using FiniteElement Analysis (FEA) has been conducted to illustrate the temperature distribution, distortionand residual stress field developed in the weldment.

10.4 Laser Based Cutting of Inclined Slots in Copper Material for Microwave Antennaand Coupler Applications, Ambar Choubey, D.K. Agrawal, Ashish Tiwari*, S.C. Vishwakarma,R.K. Jain, B.N. Upadhyaya! and A.K. Nath, Solid State Laser Division, Raja Ramanna Centrefor Advanced Technology, Indore-452013, *RF and Microwave Section, Raja Ramanna Centrefor Advanced Technology, Indore-452013. Slotted array antennas and slot couplers are widelyused in microwave communication, measurements and transmission. With increase in microwavefrequency, sizes become smaller and smaller and it becomes increasingly difficult to achievepositional and dimensional accuracies in slot fabrication. Here, we report on the application ofNd:YAG laser for making slots in copper waveguide suitable for microwave antenna and couplerapplications in the X-band frequencies of microwave region. We have optimized the lasercutting process of copper substrates with our home built high peak power (5 KW) fiber deliveredpulsed Nd:YAG laser for cutting rectangular slots in the copper waveguides within ± 0.25 mmdimensional tolerances.

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10.5 Design aspects and Experimental study of Laser Assisted Oxygen cutting process,B. Tirumala Rao, Mathew S1, C.H. Prem Singh and A.K. Nath, Industrial CO

2 laser section,

RRCAT, Indore-452 013. 1 Cochin University of Science and Technology,: This paper presentsthe design aspects considered in development of laser assisted oxygen gas cutting head to carryexperimental study for addressing various engineering problems associated in the process andto understand the dynamics involved in the process. A supersonic nozzle based cutting headwas indigenously developed. And using this cutting head 25mm thick mild steel was successfullycut with an indigenously developed 3.5kW CO

2 laser. The cut edges obtained are smooth and

uniform with slight adhesion of oxidized dross at the bottom.

10.6 A Comparative study of Target Irradiance of some Potential High Power LaserSources, A .K. Razdan, Amitansu Pattanaik1 and Subhash Sanghvi, Laser Science & TechnologyCentre, DRDO Metcalfe House Delhi-110054. In this paper, we present results of a theoreticalanalysis on the effect of atmospheric attenuation and turbulence on potential high power Lasersystems operating at 1.3mm, 3.8mm and 10.6mm wavelengths. The target irradiance for each ofthese wavelengths is estimated for propagation ranges up to 5km. The effect of transmitteraperture size on the laser spot area on the target is also studied. Results of our analysis will bepresented in the paper.

10.7 Laser processed composite layer with in-situ synthesized TiC-SiC reinforcement,M. Jamal Mohamed Jaffar1, D. Sastikumar2, P. Rajarajan1, S.Sureshkumar1, R.Sathyaraj1, HarishKumar3 and A.K. Nath3, 1Jamal Mohamed College, Tiruchirappalli, 2NIT, Tiruchirappalli, 3

RRCA T, Indore. While laser treating an Al-Si alloy precoated with Ti-Cr-SiC powders TiC wasfound to occur through in-situ synthesis and the layer consisted of TiC-SiC ceramicreinforcements. Thermal diffusivity sequence of Ti-Cr-SiC and the Al-Si alloy enabled theelimination of shrinkage cavities in the interface as well as unmelt/partially melted Cr. Preferentialformation of TiC has eliminated Al

4C

3.An eleven fold increment in hardness - 975HV was

observed.

10.8 Laser assisted decontamination- a wavelength dependent study, J. P. Nilaya, A.Kumar*, P. Raote and D. J. Biswas, Laser and plasma Technology Division, BARC, Mumbai*Advanced Fuel Fabrication Facility, BARC, Tarapur. We have carried out wavelength dependentstudy of laser assisted decontamination of metal surface. The coherent light with smallerwavelength has been found to yield the highest decontamination factor.

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11. LASERS IN CHEMISTRY, BIOLOGY AND MEDICINE

11.1 A Comparative Study of Mixed Stone and Black Pigment stone using Laser-Induced Breakdown Spectroscopy, Vivek K. Singh, A.K. Rai, S.N. Thakur1,and RanjanaSrivastava2, Laser Spectroscopic Research Laboratory, Department of Physics, University ofAllahabad, Allahabad-211002, 1Department of Physics, Banaras Hindu University, Varanasi-221005. 2Cooper Road, Civil Lines, Allahabad. We have a along term program to study themalignant and non-malignant human tissues by using Laser-induced breakdown spectroscopy(LIBS). In the present paper, we will present the result of the LIBS spectra of different types ofhuman gallstone. The LIBS spectra of different gallstone (Mixed stone and pigment stone) havebeen recorded. Our results show that the different gallstone can be identified on the basis oftheir characteristic LIBS spectra.

11.2 Photochemotherapy in the treatment of psoriasis, B. H Pawar, Dr. S. S. Arsad*,S. S. Arsad, K. P. Kadam, S. K. Devade, N. S. Mahalle, B. S. Munde, D. K. Kendre and G.G.Muley, Dept. of Physics, Sant Gadge Baba Amaravati University, Amaravati-444 602.*Dermatologist, ‘Darpan’ Skin and Cosmetic laser clinic, Akola. Our group concentrate onpatients suffering from psoriasis and study the potential of UV laser light in the treatment of thedisease. Patient was administered different combination therapies with various topical agentsapplied on the affected portion of the patient. The psoriatic lesion of face of the patient wasexposed to nitrogen laser beam for about ten seconds corresponding to 50 pulses. The dose wascontinuously increased by increasing number of pulses by 50 per day. The increase in dose wasstopped when erythema occurred at about 1100 pulses within about 4 minutes. The nitrogenlaser delivers about 3.45 J of total energy during this period. The dose was continued for 23consecutive exposures for 46 days.

11.3 Study of phototherapy with pulsed uv nitrogen laser for repigmentation insegmental type vitiligo, B. H. Pawar, Dr. S. S. Arsad*, S. S. Arsad, K. P. Kadam, B. S. Munde,N. S. Mahalle, M. N. Rode, G. G. Muley and P. B. Minase, Dept. of Physics, Sant Gadge BabaAmaravati University, Amaravati-444 602 *Dermatologist, ‘Darpan’ Skin and Cosmetic laserclinic, Akola. A patient having about 8 patches of vitiligo reported to the laboratory. It was decidedto treat the 3 spots using narrowband UVB radiation, 3 with nitrogen laser and remaining 2 werekept untreated and were utilized as control patches. It was observed that the patches treated withUVB radiation and the nitrogen laser beam shows considerable pigmentation. It was also foundthat the lesions treated with nitrogen laser show slightly more pigmentation.

11.4 Proteomics based spectroscopy study of clinical samples of cervical cancer: SerumBiopsy tissue and Pap smear, Sujatha, Lavanya Rai2, Prathap Kumar2 , BR Krishnanand3 ,KK Mahato , VB Kartha4, and Santhosh C, Center for Laser Spectroscopy, MAHE Life ScienceCentre, 2Department of OBG 3Department of Pathology, Kasturba Hospital, Manipal Academyof higher Education (MAHE) Manipal,. 42l Udayagiri Sion-Trombay Road Deonar, Mumbai –400 088. Among the main cancers of affecting female, cervical cancer is the leading cause ofcancer mortality in the developing countries1. More than 85% of all cancers are of epithelialorigin (carcinomas), and cervical cancer falls under this class 2. Regular screening by Pap smeareffectively lower the risk of precancerous changes developing into invasive cervical cancer byearly detection. Optical methods and proteomics investigations, because of their high sensitivities,are becoming promising approaches for early detection of many diseases, which are clinicallysilent for long periods.

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11.5 Rotational dynamics of a polar laser dye, J. R. Mannekutla, D.A. Nadagouda, B. G.Mulimani# and S. R. Inamdar, Laser Spectroscopy Programme, Department of Physics, KarnatakUniversity,Dharwad-580003, #Vice-Chancellor, Gulbarga University, Gulbarga-585106. Steady-state fluorescence anisotropy was measured for a laser dye coumarin 307 in series of alcoholsand alkanes. From these values, rotation correlation times (t

r) were obtained and discussed in

the light of SED hydrodynamic theory. It is observed that C307 follows stick boundary conditionat low viscosity (h) both in alcohols and alkanes and a subtle change at higher h is noted.

11.6 Confocal Laser Scanning Microscopy Study of Binary Colloidal Alloy, SidharthaS. Jena, K.P.V. Sabareesh and B.V.R. Tata, Materials Science Division, Indira Gandhi Centrefor Atomic Research, Kalpakkam 603 102. Phase separation of binary alloys was investigatedusing confocal laser scanning microscopy. The 90:10 ratio binary alloy having a total volumefraction of 0.023, shows the co-existence of poly-crystallites of 486 nm polystyrene (PS) particleswith aggregates of 100 nm PS particles whereas 50:50 ratio shows the co-existence of smallcrystalline regions of 486 nm PS particles with crystalline regions of 100 nm PS particles. Thecrystalline structure of 486 nm PS particles alone at the same volume fraction characterized tobe body-centered-cubic.

11.7 Phtotohemolysis of human erythrocytes using TiO2 nanoparticles, K. S.Meena#, S.Sivabalan$, T.Venkataraman*, V.Murugesan+, P.Aruna$ and S.Ganesan$ #Department ofChemistry, Queen Mary’s College, Chennai,*Department of Chemistry, Adhiparsakthi Collegeof science, Kalavai, +Department of Chemistry, Anna University, Chennai, $Department ofPhysics, Anna University, Chennai. Quantum size TiO

2 particles were prepared by the hydrolysis

of Titanium(IV)isopropoxide in the presence of ultrasonic waves. They were characterized byabsorption and fluorescence spectra, XRD, HRTEM and AFM techniques, and it revealed thattheir size is below 5nm. Since photoexcited TiO

2 nanoparticles are capable to drive various

chemical reactions due to their strong oxidizing and reducing ability and considering the factthat erythrocytes serve as model cells, molecular mechanism of PDT was studied using TiO

2-

QDs.The percentage hemolysis increased with the increase in TiO2 concentration and light

dose. The effect of scaventures viz., GSH and NaN3 showed that there is formation of a

considerable amount of reactive oxygen species, which is responsible for cell death.

11.8 Estimation of ground and excited state dipole moments of coumarin 440 in binarymixtures, B. R. Gayathri#, J. R. Mannekutla and S. R. Inamdar, Laser Spectroscopy Programme,Department of Physics, Karnatak University, Dharwad –580 00, #Department of Physics, J. S.S College, Dharwad-580 004. The ground and excited state dipole moments of a laser dyecoumarin-440 (7-diethylaminocoumarin) have been determined by employing solvatochromicshift at room temperature in binary solvents (DMSO + water) of varying polarities. It is observedthat the excited state dipole moment is higher than that of ground state.

11.9 Prediction of Radiotherapy Response in Cervix Cancer by Raman Spectroscopy;K. Maheedhar1,2, B. M. Vadhiraja2, Donald J. Fernendes2, V.B. Kartha1, C. Murali Krishna1

and M.S.Vidyasagar2. 1. Center for Laser Spectroscopy, 2. Dept. of Radiation Oncology, MAHE,Manipal-576104. In this study, we explore the prediction of tumor response to radiation incervix cancer using tissues collected after 2nd fraction of radiation. Based on immediate responseto treatment, subjects were categorized into three groups (complete response, partial responseand no response). Results of discrimination analysis (Score of factor, Mahalanobis distance,Spectral residual and limit test) show good correlation with clinical findings.

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11.10 Protein profile study of breast tissues by HPLC-LIF; K. Kalyan Kumar,2, M.V.P.Chowdary,2, J. Kurien2 , Stanley Mathew3, Chethan Anand, Keerthi and C.Murali Krishna,Centre for Laser Spectroscopy, 2Dept. of Surgical Oncology, 3.Dept. of General Surgery, MAHE,Manipal. Chromatograms of normal, benign, malignant and after therapy breast tissues, obtainedby HPLC-LIF, showed significant differences. PCA which was used for discrimination couldresolve clusters of normal and malignant tissues, but, benign and after therapy show minoroverlap with normal and malignant clusters, respectively. Further, analysis using Mahalanobisdistance and spectral residuals as discriminating parameters produced clear classification oftissue types.

11.11 Spatially Resolved Fluorescence Technique for Depth Resolved IntrinsicFluorescence Measurements from Two Layered Phantom, Rohit B. Patel, M. Anil Kumar,Prashant Shukla and Asima Pradhan, Department of Physics and Centre for Laser Technology,I.I.T Kanpur, Kanpur – 208016. In fluorescence spectroscopy, several techniques have beendeveloped to extract the intrinsic fluorescence and to decouple the effects of wavelengthdependent scattering and absorption from the true fluorescence. In this paper we present theresults of a study conducted to investigate the efficacy of using the extracted intrinsic fluorescencefor depth information against that of the bulk fluorescence using a two layered turbid medium.These results demonstrated that the depth information on fluorescence can be acquired moreaccurately from the intrinsic fluorescence compared to bulk fluorescence which can also decouplethe overlapping fluorescence bands from the two layers.

11.12 Monitoring Biochemical Changes in Normal and Cancerous Cervical Tissues UsingIntrinsic Fluorescence, Md. Ejaz A. Lodhi, Prashant Shukla,Anjali Saini, Meena Pal, MonikaMishra Nidhi Agrawal, Asha Agarwal and Asima Pradhan, Department of Physics and Centrefor Laser Technology, I.I.T Kanpur, Kanpur – 208016. Development of techniques to extractdiagnostically relevant biochemical information is the need of the hour and several groups areworking towards this. Here we report the results of a study conducted to explore possibility ofdiscriminating normal and cancerous cervical tissues on the basis of the observed spectraldifferences in the collagen intrinsic fluorescence band from the normal and the cancerous tissues.In a study with limited number of cervical tissue samples it is observed that intrinsic fluorescenceis a better detection technique as compared to the co-polarized fluorescence and indicates adecrease in collagen fluorescence in tumors.

11.13 Hyper-Rayleigh scattering (HRS) and continuum generation of salt inducedaggregates of Silver nanoparticles (AgNPs): The effect of cation size (Li+, Na+ and NH4

+),K. Das, A. Uppal, and P. K. Gupta, Bio-Medical Applications Section, Raja Ramanna Centrefor Advanced Technology, Indore-452013. The HRS intensities of AgNPs were greatly enhancedon addition of NaCl and NH

4Cl (50 & 200x respectively), upon addition of LiCl this enhancement

was rather modest (~4x). Continuum generation was also observed only from NaCl and NH4Cl

induced aggregates. These observations suggest that smaller size and hence higher ionic chargedensity of the Li+ ion is not conducive to the formation of aggregates.

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11.14 Fluorescence resonance energy transfer between DPH and Nile Red in a lipidbilayer, B. Jain and K. Das, Bio-Medical Applications Section, Raja Ramanna Center ForAdvanced Technology Indore-452013. FRET between the well-known membrane binding probesDPH and Nile Red is investigated in a lipid bilayer. A ~ 60% FRET efficiency was observedfrom the steady state experiments whereas, time resolved experiments with limited time resolution(200 ps) provided a lower (~20%) FRET efficiency. The emission of Nile Red, was observed torise with a time constant of 670 ps which is attributed due to FRET. Our results indicate thatDPH and Nile Red may have the potential to be used as a FRET pair to monitor lipid bilayerorganization.

11.15 Monitoring of Blood Hemolysis by Small Angle Light Scattering Spectroscopy,M.K. Swami, P. Buddhiwant, S. Manhas, A. Uppal, N. Ghosh and P.K. Gupta, BiomedicalApplications Section, Raja Ramanna Centre for Advanced Technology, Indore-452013. In thispaper, we present a method based on small angle elastic scattering spectroscopic measurementsfor monitoring of hemolysis in red blood cells (RBCs). The approach exploits the signature ofhemoglobin absorption in the elastic scattering spectra recorded at appropriately chosen scatteringangle, to accomplish this objective. The results of the experimental studies and the theoreticalinvestigations demonstrated that the scattering spectra recorded at angles corresponding to thesecond maxima (scattering angle ~ 6o) of the angular scattering pattern of RBCs, bears minimalsignature of hemoglobin absorption when the cells are in intact form. In contrast, the spectrafrom the hemolysed RBCs showed prominent features of hemoglobin absorption. The spectralfeatures of the elastic scattering signal recorded at this angle was therefore used for quantitativedetection of percentage of hemolysis in RBCs.

11.16 Nine Element Mueller Matrix for Tissue Diagnosis, S. Manhas, M.K. Swami, P.Buddhiwant, N. Ghosh and P.K. Gupta, Biomedical Applications Section, Raja Ramanna Centrefor Advanced Technology, Indore – 452013. In this paper, we present the results of our studieson the measurement of nine element (3 ´ 3) Mueller matrix on normal and malignant (squamouscell carcinoma) tissues resected from human oral cavity. A method based on polar decompositionof Mueller matrix was developed and used for quantification of the wavelength dependence ofthe different polarization parameters, namely, the linear retardance (d, difference in phase betweentwo orthogonal linear polarization states ), the linear diattenuation (d, different attenuationcoefficients of two orthogonal linear polarization) and the linear depolarization coefficient (D)of normal and the malignant tissue samples. The results showed significant differences in thevalues for d (l ) and d (l ) between the normal and the malignant tissues that can be exploited forquantitative tissue diagnosis.

11.17 A view-based approach for the reconstruction of optical properties of turbid media,H.S Patel, A. Srivastava and P.K. Gupta,. Biomedical Applications Section, Raja RamannaCentre for Advanced Technology, Indore-452013. A view-based approach for the computationof updates of the optical parameters of a turbid medium has been discussed. The approachdiffers from most of the iterative reconstruction techniques currently in use in terms of theimplementation of updates of the optical parameters obtained after each iteration. Results of thesimulation studies in frequency-domain at a modulation frequency of 400 MHz have beenpresented.

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11.18 Fluorescence Induction Kinetics of Arhar Plants to Detect the Effect of Zinc Metalvia LIF technique, Renu Maurya, Richa Bhargava* and R. Gopal, Laser and SpectroscopyLaboratory, Department of Physics, *M. N. Saha Centre of Space Studies, IIDS University ofAllahabad, Allahabad-211002.

11.19 Sorting and Guiding of microscopic objects with evanescent optical field, R.Dasgupta, S. Ahlawat, A Uppal and P. K. Gupta, Biomedical Applications Section, Raja RamannaCentre for Advanced Technology, Indore-452 013. We report the use of evanescent optical fieldfor sorting and guidance of microscopic objects. The approach exploits the fact that the opticalevanescent field created at total internal reflection of a laser beam at an interface can exert forceon microscopic objects situated near the interface. Further, when particles are suspended in afluid above an interface, those with higher effective mass tend to reside at a shorter averageheight from the interface. Since evanescent optical field diminishes rapidly with increasingheight from the interface, the force that it will exert on the particles suspended in a fluid abovean interface will depend on their mass. We have exploited this dependence to sort polystyrenemicrospheres having different diameters.

11.20 Synchronous fluorescence spectroscopic characterization of DMBA inducedepithelial pre-cancers in mice, J. Ebenezar1*, P. Aruna1 and S. Ganesan1, 1Division of MedicalPhysics/Lasers, Department of Physics, Anna University, Chennai. *Department of Physics,Jamal Mohamed College, Tiruchirappalli. In the present study, Synchronous fluorescencespectroscopic (SFS) technique was used to characterize the DMBA induced epithelial pre-cancers in mice. The normal and different tissue transformation conditions, shows distinct peaksobserved at 297, 360 and 386 nm may be attributed to tyrosine and tryptophan residues, structuralproteins collagen and elastin, and NADH respectively.

11.21 Laser induced breakdown spectrometry (LIBS) for the determination of traceimpurities in Thoria, D..Alamelu, A.Sarkar and S.K.Aggarwal, Fuel Chemistry Division,Bhabha Atomic Research Centre, Trombay, Mumbai-400 085. LIBS with Nd-YAG laser (1064nm), 10 Hz repetition rate, 60 mJ energy and a delay of 3.5 ms for data acquisition was used fordetermination of trace constituents in thoria matrix without dissolution or separation of impuritiesfrom thorium matrix. Calibration curves were obtained for some of the impurities usingindigenously developed thoria based CRMs. Using one CRM as unknown, an agreement ofabout 15 % was obtained with the expected values for impurities concentartions.

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12. LASER BASED INSTRUMENTATION

12.1 Results of diode laser based optical current sensor, Rohit Shukla, A. Shyam and PulsedPower Group Institute for Plasma Research, Bhat, Gandhingar, Gujarat. A prototype of currentand magnetic field measurement sensor, based on well known Faraday rotation principle is presentedhere in this paper. We have measured 7.5kA of currents with 100ns rise-time which is limited byphotodiode circuit not by photodiode which has 2ns minimum rise time. Polarized light comingfrom solid state diode laser is directly coupled to the optical fiber which has magneto-opticproperties. Faraday rotation caused by external magnetic field is measured using analyzer andphoto-diode.

12.2 A flashlamp current monitoring system for two-beam Nd: glass laser chain, H.R.Bundel and C.P. Navathe, Laser Plasma Division, Raja Ramanna Centre for Advanced Technology,Indore-452 013. The flashlamp current monitoring system is very essential in the high powerlaser chains to ensure the reliable operation of the same. It measures the current pulse of each pairof the flashlamp using a current transformer and graphically displays the same on the PC by usingcurrent monitor software developed in Labview. This in turn can be used to analyze flashlampcurrent pulse amplitude, time, shape and delay between any two current waveforms.

12.3 Optical detection of partial discharges in a high voltage equipment Using He-NeLaser, S. Karmakar 1, N. K. Roy and P. Kumbhakar1 Dept. of Electrical Engineering, NationalInstitute of Technology, Durgapur-713209, 1Dept. of Physics, National Institute of Technology,Durgapur-713209. The online monitoring of partial discharges (PDs) in high voltage equipmentis required to access the insulation quality. An optical detection technique has been proposed forthe detection of the PDs in a transformer oil test cell.

12.4 Simulation of Parametric Performance of a Doppler Wind Lidar, Deepak K Dubey,S. Veerabuthiran, J .P. Dudeja and M K Jindal, LASTEC, DRDO, Delhi – 110 054. Simulationstudy has been carried out to optimize the performance of a Nd: YAG laser-based direct detectionDoppler wind lidar. Factors like lidar return signal, laser linewidth, etalon passband etc. havebeen considered for this study. An accuracy of 0.5- 0.8 ms-1 has been achieved by using single anddouble etalon as filters in the measurement of wind speed up to an altitude of 5 km with 30-mrange resolution.

12.5 Laser Radar in exploring the cirrus cloud climatology at a tropicalcoastal stationTrivandrum, India, R.Sreeja, S.R.Radhakrishnan, M.Satyanarayana, S.Muraleedharen Nair,B.Presennakumar and S.V. Mohankumar, Space Physics Laboratory, VSSC, Trivandrum-695022.Laser Radar – Lidar has been established as a promising tool in the remote sensing of aerosols andcloud layers in the atmosphere and in obtaining the altitude profiles of aerosol extinction coefficientwith very fine altitude resolution. The objective of the present study is to construct a cirrusclimatology using ground based laser radar measurements over the tropical coastal stationTrivandrum with fine altitude resolution. The Lidar system designed and built in house is capableof detecting the presence of even sub visual, thin and thick cirrus clouds and their multi layerstructure with fine altitude resolution and in exploring their temporal evolution in the desired timescale. Seven Years of ground based lidar measurements taken during the period 1999 to 2005 isanalyzed to get the cirrus cloud climatology for this tropical coastal station.

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12.6 Interferometric refractive index measurement of graded index polymer opticalfibre preform, M.Kailasnath1, Bikas Ranjan2, P.Radhakrishnan1, V.P.N.Nampoori1 andC.P.G.Vallabhan2, 1International School of Photonics2, Center of Excellence in Lasers andOptoelectronics Sciences, Cochin University of Science and Technology, Kochi-682 022. In thispaper we discuss the refractive index measurement of three different types of graded indexpolymer preforms fabricated by the interfacial gel polymerization method for polymer opticalfiber based applications. The preform is a cylinder of polymer whose refractive index distributioncan be made to coincide with that desired for the core of the polymer optical fiber. To obtain anyparticular refractive index profile in the core of the optical fibre along the radial direction, apolymer rod (preform) with the desired profile has to be fabricated. Three types of graded index(GI) poly (methyl methacrylate) (PMMA) rods were prepared by incorporating large moleculesgiving high refractive index, viz; Diphenyl phthalate (DPP), Benzyl Butyl Phthalate (BBP) andBenzyl benzoate (BEN) during the second phase of polymerization. The refractive index profilesof the rods were measured by interferometric technique and the values of the index exponentswere obtained. The calculated values of the profile parameter a, are 1.48, 1.56 and 1.63 forperforms with dopants DPP, BBP and BEN respectively.

12.7 Time evolution of Optical Patterns at the diffusion region in the ChristiansenFilter, R. Mahanta, Jeena Das1, Chandan Siam, Mitali Konwar and G.D. Baruah, Laser andSpectroscopic Lab, Dept of Physics, Dibrugarh University,Dibrugarh-786004, 1PhysicsDepartment, Bahana College, Jorhat. In the present work we have studied the interferencefringe pattern and its time evolution observed in the diffusion region separating two liquids in aChristiansen cell using laser. It has been observed that there is a definite co-relation between theshape of the fringe pattern and the width of the diffusion region. The time evolution of thisfringe patterns indicates that as diffusion region increases the circular fringe becomes ellipticaland finally straight. It is believed that a detailed investigation of these diffusion fringes willthrow much needed light not only on the theory of the Christian effect but also on the rate ofdiffusion between two molecules.

12.8 Maxwell-Boltzman distribution Patterns exhibited by Dynamic InterferenceFringes in Liquid Phase, Chandan Siam1,Rajib Mahanta, Mitali Konwar, N.C. Sarmah andG.D. Baruah, Department of Physics1, L.T.K. College, Azad, N. Lakhimpur-787001, Departmentof Physics, Dibrugarh University, Dibrugarh-786004. In the present work we have investigatedthe nature of dynamic interference fringes which are observed when a transparent orsemitransparent liquid contained in a sample cell is illuminated with the help of a He-Ne Laser(6328Å) or a Ar+ Laser (blue – green) and the image of the transmitted beam is projected on ascreen at a distance of 3m from the sample cell. We have used liquid with different colloidalsuspensions of different materials in usual solvents. The distribution of speeds in various numbersof fringes has been worked out and it has been found to be of Maxwell-Boltzman type. We haveused twelve different samples in the liquid phase and the nature of dynamic interference fringeshave been studied in each case.

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12.9 Data Acquisition System for Optical Densitometer, Anand Valecha, Viraj Bhanageand A.G.Bhujle, Instrumentation and Control Division, Raja Ramanna Centre For AdvancedTechnology, Indore-452013. A Laser diode based Optical Densitometer is developed, which isused for the measurement of relative density/dose information. The laser beam is recorded on aphotographic film and then this film is scanned to measure the optical transmission and dose.Output is presented as relative voltage, representing optical density expressed as a percentageof user selectable maxima.

12.10 FTIR Analysis of SiON films for Photonics Wave-guide Applications, V. K. Tomar,L. S. Patil and D. K. Gautam, Department of Electronics, North Maharashtra University, Jalgaon-425001. In present work, the organic precursor hexamethyldisilazane (HMDS) has been usedfor the first time as a source of silicon to deposit silicon oxynitride thin films using thermalCVD system. The ammonia (NH

3) and oxygen (O

2) have been used as a source nitrogen and

oxygen respectively. The deposited silicon oxynitride films have been characterized by usingthe Fourier transform infrared (FTIR) spectroscopy (8400-Shimadzu). It was observed that withincrease in deposition temperature, the position of Si–O-Si stretching peak moves toward lowerwave number i.e. 1078.2 –1068.5 cm-1. It was also found out that the Si-OH and N-H bothabsorption peaks are disappear from the absorption spectra. This may be due to the decrease oftotal bonded hydrogen concentration in the deposited films.

12.11 Observation Of Anomalous Optogalvanic Effect in Negative Glow Region Of NeonMiniature Indicator Lamp, V.K Saini, V.K Shrivastava and R. Khare, Laser SystemsEngineering Division, Raja Ramanna Centre For Advanced Technology, Indore-452 013.An anomalous optogalvanic effect in a negative glow of a neon discharge produced in a miniatureneon indicator lamp is described in the negative resistance region (dv/di <0). Previous studies[1] were confined to dv/di > 0 region only. Here, it is the negative resistance of the dischargethat is responsible to the anomalous behavior of the normal optogalvanic signal. A mathematicalmodeling of the equivalent electrical discharge circuit in presence of tuned laser radiation to theatomic spices of the discharge may throw more light on the useful aspect of the abovephenomena.

12.12 Development of temperature sensor using UV CVL written (255 nm) fiber Bragggratings, O. Prakash, R.. Mahakud, S. K. Dixit, P. Saxena, V. K. Dubey and U. Nundy, LaserSystem Engineering Division, Raja Ramanna Centre for Advanced Technology, Indore-452013.This paper reports the development of temperature sensor using fiber Bragg grating writtenwith 255 nm UV CVL. A Bragg grating of 7.0 dB reflectivity written with the phase mask isused for the sensor development. As the temperature of the FBG is increased the reflectedcentral Bragg wavelength shifted to longer wavelength side. Temperature sensitivity of 0.01nm/0C is observed.

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12.13 High resolution Raman Lidar for simultaneous measurement of temperature andwater vapor in the lower atmosphere at a Coastal station, Trivandrum (8°33’N, 77°E),Satyanarayana M1, Bindhu R1, Radhakrishnan S R2 Presennakumar B1, Murty V S 2 andSreeja R1, Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum-695 022,2Indian Institute of Technology (Madras), IIT Campus, Chennai-600 036. High resolution Ramanlidar in the Space Physics Laboratory, Vikram Sarabhai Space centre, Trivandrum is capable ofmonitoring atmospheric temperature and water vapor near simultaneously. Simultaneousmeasurement of atmospheric temperature and water vapor are needed for basic studies onatmospheric processes and meteorological studies. Here we report on a vibrational-rotationalRaman method to derive temperature and water vapor mixing ratio from atmospheric nitrogenand water vapor. The preliminary results obtained are presented in this paper.

12.14 Simulation of optical analogue to digital conversion and digital to analogueconversion scheme, V. Bhat, G. Soni, P.Sen, and P.K. Sen, Department of Applied Physics,SGSITS, Indore-452 001. We have simulated an Optical A/D conversion scheme using LABVIEWsoftware, which has the potential to be commercially employed in the present opticalcommunication systems. The proposed optical A/D conversion is based on the electro-opticphase modulator and it is the simplicity of the code generated which makes it different from theearlier proposed schemes. The output code generated here is the “thermometer code” which issimilar to that of the electronic flash ADC and hence can be easily decoded using conventionalmethods.

12.15 A 120kW Switch Mode Programmable Power Supply for 10kW Transverse FlowCW CO2 Laser, T. Reghu, D.D. Saha, M.O. Ittoop, and A.K. Nath, Industrial CO

2 Laser Section,

Raja Ramanna Centre for Advanced Technology, Indore-452013. This paper describes an off-line 120kW switch mode programmable power supply (SMPS) for 10kW transverse flow CWCO

2 laser. The power supply’s output current can be programmed for three different modes

namely (i) Continuous mode (ii) Pulsed periodic mode (iii) Retriggerable single shot mode.Power supply has been developed on the basis of modular concept i.e. two numbers of 60kWSMPS are connected in series to increase the output voltage. Each module delivers 1.5 kV and40 Amps, therefore, the combined output rating is 3.0kV and 40Amps. The SMPS has amodulation bandwidth of ~2.0kHz. The full load efficiency of 95% has been achieved.

12.16 Software development for automation of spectroscopy experiments, Nakul Mudgal,T. K.Sharma, S.Porwal and A.K.Nath, Solid State Laser Division, Raja Ramanna Centre forAdvanced Technology, Indore-452 013. This article presents a software tool developed inLabVIEW for automatic data acquisition, logging and presentation of spectroscopy experiments.Development involves interfacing of instruments like Monochromator, Lock-in amplifier andTemperature controller of different make and a controller developed in house. Drivers for theseinstruments are developed and integrated and a user-friendly application program has beendeveloped for extended data logging and graphical presentation.

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12.17 Development of a low noise level photo-detector, S. Singh, S. Krishnan, A. Raya, V.B. Tiwari, H. S. Rawat and S. C. Mehendale, Laser Physics Applications Section, Raja RamannaCenter For Advanced Technology, Indore-452013 aLaser and Plasma Technology Division,Bhaba Atomic Research Centre, Mumbai-400085. We have developed a compact, easy-to-useand cost effective photo-detection system for measuring a few nano watt optical signals. Thedetector circuit consists of a photodiode pre-amplifier stage, a difference amplifier stage and ahigh gain instrumentation amplifier stage. The photo-detection system was calibrated with thehelp of standard power meter and the calibration factor in the linear range was obtained about25mV/nW for continuous light level.

12.18 Development of automation software for LI characterization facility for laser diode,Chirag Gupta1, Nakul Mudgal2, S. Porwal2, T. K. Sharma2, Viraj Bhanage3, H. Khatwani4 andA. K. Nath2, 1Institute of Engineering and Technology, DAVV Indore-452 017, 2Solid StateLaser Division, 3Instrumentation and Control Division, 4Power Supply Division, Raja RamannaCentre for Advanced Technology, Indore-452 013. This article presents a software programdeveloped in LabVIEW for automatic data acquisition, logging and presentation for LIcharacterization facility for laser diodes. In the setup there are instruments like power meter, anindigenous laser diode driver and an analog data acquisition module.

12.19 Better handling of reverse-recovery charge of switching diode in pulsed powersupply for flash-lamp-pumped solid-state-lasers, Sajith Kumar.T.R, R. Arya, Manoj Kumarand A. K. Nath, Solid State Laser Division, Raja Ramanna Centre for Advanced Technology,Indore 452 013. The reverse-recovery charge mechanism of high-voltage high-current diodescauses unwanted ringing and high-voltage spikes in the circuits. In this paper, reduction achievedin ill effects of reverse recovery charge of switching diode in pulsed power source for flash-lamp-pumped solid-state-laser is reported with some experimental results.

12.20 Development of a battery operated handheld power meter for a cw and pulsedfemto second laser, S. Krishnan, V.P. Bhanage*, K.S.Bindra and S.M.Oak, Ultrafast StudiesSection, *Instrumentation and Controls Division, Raja Ramanna Center For AdvancedTechnology, Indore-452013. A chargeable 9V battery operated handheld power meter based ona photo diode, an amplifier, a micro-controller and LCD was developed with battery voltagemonitoring circuits. The instrument was used to measure the power of a CW diode laser of 642nm and a 82MHz pulsed femto second laser of 794nm. The dynamic range obtained for CW andpulsed laser are about 2000 and 10700 respectively.

12.21 Fiber-optic mid-infrared laser sensors and spectroscopy for the detection ofexplosives, Ashwini Kumar Sharma1, Wolfgang Schade1,2, Sandra Börner1,2 and Claus Romano1,1Technische Universität Clausthal, Institut für Physik und Physikalische Technologien,Leibnizstrasse 4, 38678 Clausthal-Zellerfeld, Germany, 2Technische Universität Clausthal,LaserAnwendungsCentrum, Arnold Sommerfeld Strasse 6. 38678 Clausthal-Zellerfeld, Germany.Mid-infrared (MIR) absorption spectroscopy is used to detect TATP and other explosives. MIRwavelength is generated by difference frequency generation (DFG) technique. A single rotationalline of evaporated TATP is detected at 8.05 µm at room temperature. A TATP concentration of100 ppm is obtained.

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13. LASERS IN MATERIAL SCIENCE

13.1 Atomic force Microscopy Study of Nanocrystalline Tungsten Oxide Thin filmsPrepared by Pulsed Laser Deposition Technique, Lethy.K.J, Beena.D, VinodKumar. R andV.P.Mahadevan Pillai, Department of Optoelectronics, University of Kerala, Kariavattom,Trivandrum, Kerala. Nanocrystalline thin films of tungsten oxide has been prepared by reactivepulsed laser deposition technique on glass substrates at different substrate temperatures and ambientoxygen pressures. Using contact mode atomic force microscopy, the growth process andmicrostructure of WO

3 nanocrystalline films were investigated. Dependence of surface roughness

and crystalline grain size on deposition conditions were also studied in detail.

13.2 Preparation and characterization of Pulsed Laser Deposited BaWO4 thin films,

Venugopalan Pillai.N,, Lethy.K.J and V.P. Mahadevan Pillai, Department of Optoelectronics,University of Kerala, Kariavattom, Trivandrum, Kerala-695581. Thin films of barium tungstate(BaWO

4) on quartz substrate were prepared by Pulsed Laser Ablation technique using a Q- switched

Nd: YAG laser (Quanta – Ray INDI – series, Spectra Physics) with 200 m J of laser energy at 532nm The films were annealed at temperatures of 6000C 8000 C and 10000C for 3 hours andcharacterized by X-ray diffraction (XRD), UV-VIS spectroscopy and scanning electron microscopytechniques. Crystalline nature and optical properties of the films are investigated

13.3 Nanoparticle formation in vacuum using sub-nanosecond laser pulses, U. Chakravarty,P. A. Naik, H. Srivastava, C. Mukherjee, M. K. Tiwari, H. Singhal, V. Arora, J. A. Chakera, R. V.Nandedkar., P.D.Gupta and R.A. Ganeev1, Laser Plasma Division, Raja Ramanna Centre forAdvanced Technology, Indore-452013. 1Akadempribar Scientific Association, Tashkent 700125,Uzbekistan. We show that by laser ablation of the bulk material in vacuum, under appropriatefocusing condition, one can obtain stable nanoparticles of defined sizes. The target used weresilver, indium, chromium etc. and analysis of the nanoparticles was done by SEM, TXRF, AFMand TEM. Using sub-nanosecond laser pulses, we show that the nanoparticle formation dependssolely on the laser intensity irrespective of the target material.

13.4 KrF Excimer Laser Induced quarter micron Periodic Structure on Polymer Surface,P. Bhatnagar1, C. Mukherjee2 and U. Nundy1, 1Chemical and Excimer Laser Section, 2Laser Systemand Engineering Division, Raja Ramanna Centre for Advanced Technology, Indore-452013. Laserinduced periodic structures of quarter micron size are produced on polyethylene terephthalate(PET) using the polarized beam of KrF excimer laser. These structures are produced at a fluence of~ 4mJ/cm2 much below the ablation threshold of the polymer film. The obtained relief is studiedusing an atomic force microscope.

13.5 Characteristics of laser pierced holes in pulsed mode and power ramped pulsed mode,B. Tirumala Rao, Sanjeev Kumar1, and A.K. Nath, Industrial CO

2 laser section, RRCAT, 1DAVV,

Indore-452 013. The paper presents the characteristics of the pierced holes carried on steel sheetsin pulsed mode (PM) and power ramped pulsed mode (PRPM). Laser piercing experiment wascarried out for 0.5mm, 1.5mm & 3mm thick mild steel and 1mm & 3mm thick stainless steelsheets with a 4 kW (CW/PM) indigenously developed CO

2 laser. For the same pulse parameters, in

PM the hole size at top and bottom was comparatively large to that obtained in PRPM. At a givenduty cycle, the hole size was decreasing with increase in pulse frequency. A significant improvementin pierced hole quality was achieved by ramping the laser power in pulsed mode.

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13.6 Laser Surface Melting of AISI 304 Stainless Steel for Enhanced IntergranularCorrosion Resistance, Sandip Mahajan1, P.Ganesh, K N Adhe2, Rakesh Kaul, Vivekanand Kain2,R. C Prasad1 and A. K. Nath, Raja Ramanna Centre for Advanced Technology, P.O. CAT,Indore-452 013. 1Department of Metallurgical Engg. & Materials Science, Indian Institute ofTechnology, Mumbai. 2Materials Science Division, Bhabha Atomic Research Centre,Mumbai400 085. Laser surface treatment (LSM) has been extensively employed to improve corrosionresistance of austenitic stainless steels. The objective of the present study is to improveintergranular corrosion resistance of AISI 304 SS through LSM.

13.7 Electronic Measurement of Wire Feed Rate for Laser Cladding, Ayukt KumarPathak, C. P. Paul and A. K. Nath, Industrial CO

2 Laser Section, Raja Ramanna Centre for

Advanced Technology, Indore – 452 013. A microprocessor based Electronic Device is developedto measure and display the wire feed rate. The maximum and minimum wire feed rate at whichwire is being ejected from wire feeder is measured as 2416mm/minute and 6mm/minuterespectively. The measured wire feed rate is having error coefficient of ±6% of displayed value.

13.8 Influence of Active Flux on Plasma during Laser Welding of Type 304 StainlessSteel, R. Jagdheesh, Nageshwar Singh1, P. Ganesh, M. S. Bhagat, Harish Kumar, Rakesh Kaul,H. S. Vora1 and A. K. Nath, Industrial CO

2 Laser Section, 1Laser System Engineering Division,

Raja Ramanna Centre for Advanced Technology, Indore – 452 013. Present paper investigatesplasma-suppression effect of active flux (SiO

2) during laser welding of AISI 304 stainless steel

sheet through real time photography and plasma emission spectroscopy.

13.9 Effect of Back Ground Pressure on the Structure and Surface Morphology ofPotassium Lithium Niobate thin films deposited by Pulsed Laser Ablation Technique, V.Jayasree, K. J. Lethy, R.Ratheesha, V. Ganesanb, V. P.Mahadevan Pillai, and V. UnnikrishnanNayar, Department of Optoelectronics, University of Kerala, Kariavattom, Trivandrum, Kerala,695 581, a Centre for materials for electronic Technology, Athani P. O Thrissure-680771, India.b.UGC-DAE Consortium for Scientific Research, Indore Centre, Indore. Potassium LithiumNiobate Thin films are prepared by pulsed laser ablation technique and are characterized usingXRD and AFM techniques. The optimum condition for the preparation of KLN thin films isachieved.

13.10 Real-Time Focus Control in Material Processing with Fiber Coupled Solid-stateLasers Ambar Choubey, B.N. Upadhyaya, S.C. Vishwakarma, D.K. Agrawal, Sabir Ali,R.K.Jain and A.K. Nath , Solid State Laser Division, Raja Ramanna Centre for Advanced Technology,Indore-452013. A non-contact optical method has been deviced for real-time focus control oflaser beam in material processing with fiber coupled solid-state lasers. This method also providesestimation about continuation and any interruption of cutting process during the laser materialprocessing. This method has been applied on different materials and found to be extremelyuseful in remote processing applications.

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13.11 Laser Excited Decay of Microwave Assisted ZnO Nanorings, Atul Gupta1 , DhirajKumara, Sandeep Sohal, N. K. Vermab and H. S. Bhatti, Department of Physics, PunjabiUniversity, Patiala-147 002. b SPMS, Thapar Institute of Engineering and Technology, Patiala-147004.

13.12 Laser assisted stratified alloying of Al-Si alloy with Fe-Cr-Si, M.Jamal MohamedJaffar1, D.Sastikumar2, P.Rajarajan1, P.Prakash1, D.Saravanan1, Harish Kumar3 and A.K.Nath3,1Department of Physics, Jamal Mohamed College, Tiruchirappalli. 2Department of Physics,NIT, Tiruchirappalli, 3Industrial CO

2 laser Section, RRCAT, Indore-452 013. Stratified alloying

occurs when an Al-Si substrate is laser alloyed with 20Fe-60Cr-20Si precoat under 300Jmm-2 -laser fluence (2.5kW: laser power and 0.5m/min. traverse speed). Fe increment introduces cracks.The alloyed region is found to be free from cracks and pores. SEM and EDS analyses reveal themicrostructural and microchemical variations owing to laser impact. A six fold hardness increment(505HV) is observed.

13.13 Characterization of Laser alloyed WC–Zr–Ni coating on AISI 304 SS, P. Rajarajan1,D.Sastikumar1, M. Jamal Mohamed Jaffar2, Harish Kumar3 and A.K.Nath3, 1Department ofPhysics ,NIT, Tiruchirappalli, 2Department of Physics, JMC, Tiruchirappalli,3CO

2 laser Section,

RRCAT, Indore-452 013. In this work, AISI 304 SS with preplaced WC–Zr–Ni coating waslaser treated for topological character modification. Smooth and crack free surface conditionswith enhanced hardness (750HV ) prevailed while the substrate with 60WC–30Zr–10Niprecoating was laser processed at 59 J/mm2 laser density, (2.0kW and 1.0m/min. scanspeed).Highly hardened phases (1430HV) were found in the laser treated region.

13.14 Laser cladding on AISI 316L Stainless Steel with WC-Si-Ni, A.Viswanathan, D.Sastikumar, Harish Kumar1, R.Kaul1 and A.K. Nath1, Department of Physics, National Instituteof Technology, Tiruchirappalli - 620 015, 1Industrial CO

2 laser Section, Raja Ramanna Centre

for Advanced Technology, Indore - 452 013. The study deals with laser cladding of WC-Si- Nion AISI 316L SS to improve its tribological properties. The results show that, a uniform anddefect free clad layer (300mm thick) formed over the substrate when the laser power was 1.5kWand 2.0 m/min. scan speed. The clad layer exhibits enhanced hardness about 800 HV and excellentadhesive strength with substrate.

THESISABSTRACT

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Study of medically important lasers and their applications

S.S. ARSADDept. of Physics,

Sant Gadge Baba Amaravati University,Amaravati-444 602 (Maharashtra)email : [email protected]

The UV 337.1nm nitrogen laser has high potential in the field of medical applications. It hasbeen successfully applied in the treatment of diabetic wounds, tuberculosis etc. It is also used inthe diagnosis of cancer, tumor, oral carcinoma etc. We studied the potential of the pulse UVnitrogen laser in the skin diseases like psoriasis, vitiligo, pityriasis versicolor which are moreappealing. We study application of diode laser in the hair removal which falls in the category oflasers in cutaneous and cosmetic surgery, a sub topic of dermatosurgery.

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Study of Optical Fiber Bragg Grating Solitons near the PhotonicBandgap in Resonant and Non-Resonant media

P. RAMESH BABUVIT, Vellore-632 014


The search for a new communication technology has always been the quest of human society for thebetterment of our living conditions. The communication technology is always at the forefront of allother sciences and technologies. Ever since the invention of telephone at the end of 19th century, thedissemination of information has become faster and the volume of information being transferred hasgrown exponentially. The advent of fiber optics has undoubtedly revolutionized telecommunicationsystems around the world, enabling an unprecedented amount of information exchange, all at almostan amazing speed of light. However, we are just at the beginning of what will likely to be known asphotonics century. Just as electronics dramatically improved the quality of life in the last century,photonics promises to do the same in the 21st century. One of the keys to the success of the ensuingphotonics revolution will be the use of optical solitons in fiber optic communications.

Despite the availability of extremely low loss fibers (0.16dB/km), the pulse spreading due to dispersionis the most troublesome aspect in fiber communications. This pulse spreading is very much detrimentalsince the well separated pulses from the transmitter, while propagating through an optical fiber, beginto overlap and reach the receiver with a high degree of overlapping. Hence this ultimately leads toerror like inter symbol interference in the transmitted information. However, as supported by manytheoretical and experimental results, the information in the form of solitons can ensure dispersionlesstransmission. An optical soliton is nothing but an optical pulse, which could travel several thousandsof kilometer without dispersion provided the loss in the system is taken care. The optical solitonsarise as an outcome of counterbalancing effect of pulse widening by dispersion with that of pulsecompression due to an optical nonlinear effect called self-phase modulation (SPM). Thus, scientistsall over the world have realized the importance of soliton technology that can accomplish adispersionless long distance communication.

This thesis deals with the soliton type pulse propagation in various kinds of nonlinear optical periodicmedia wherein both ideal and real world physical conditions have been considered. As alreadymentioned, the impact of nonlinearity in optical communication can ensure dispersionless transmissionand such a miracle is possible only with a nonlinear entity called optical soliton. However, in recenttimes, compared to the regular fiber solitons, there has been an increased interest towards the study ofgrating solitons, which are realized using a passive device called Fiber Bragg Grating (FBG). Thisis because, to realize the solitons in fibers, we need fibers of length about hundreds of kilometer, inorder for dispersion to counteract with SPM. Thus the generation of solitons in fibers is economicallynot viable and the technology involved is also more complicated. Basically an FBG is nothing but ashort piece (about a few cm) optical fiber in which a periodic variation in the refractive index isartificially induced by irradiating it with the two interfering beams of a high frequency electromagneticradiation such as ultraviolet radiation.

In FBG, the grating induced dispersion is exactly counterbalanced with the Kerr nonlinearity throughthe self and cross-phase modulation effects. As a result, there is a formation of slowly varying localizedenvelope in a FBG structure known as, in general, grating solitons. They are often referred to as gapsolitons if their spectra lie well within the photonic bandgap (PBG) and as Bragg solitons if their

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spectra lie close to but outside the PBG structure. Thus, based on the frequency spectrum of the pulsewith respect to PBG, solitons in FBG can be classified into two categories, namely, Bragg solitons(BS) and gap solitons (GS).

The first chapter begins with an introduction to the history of nonlinear dynamics and solitons. Inorder to discuss the formation of optical solitons in fibers, a general introduction underlying thefundamental linear and nonlinear properties of the single mode fibers is presented. After this generalintroduction, the concept of nonlinear periodic structures in fibers known as fiber Bragg gratings isdiscussed. In addition, potential applications and features of FBGs are mentioned. Finally, the derivationof the model equation for the slowly varying electric field envelope of the light wave in nonlinearperiodic structures is also presented.

The second chapter deals with the nonlinear pulse propagation in a nonlinear periodic structureconsisting of N alternating layers with different linear refractive indices and different Kerr nonlinearitieswhere the pulse propagation is governed by the nonlinear-coupled mode (NLCM) equations. Byemploying a technique known as multiple scale analysis, the generation of bright and dark Bragggrating solitons is investigated near the PBG with the higher order linear and nonlinear effects for thefirst time. The interesting and important physical parameters such as pulse width and peak power ofthese solitons have also been calculated.

In the third chapter, the influence of next higher orders nonlinearity in the aforementioned theoreticalmodel has been investigated. The interest for considering Cubic-Quintic (CQ) nonlinearity in thismodel stems from the fact that a nonlinear correction to the medium’s refractive index in the form

where I being the light intensity and the coefficients determine the

nonlinear response of the media. Although, formally it may be obtained by an expansion of the saturable

nonlinearity it is restricted under the effect of self-focusing as

However, the CQ model changes the sign of focusing at a critical intensity

An experimental measurement of the nonlinear dielectric response in the para-toluene salfonate (PTS)optical crystal aptly models the above-mentioned insights. Furthermore, it has been shown that theBragg Grating-CQ model studied in this work is meaningful in both temporal and spatial domains.For the purpose of carrying out the generation of bright Bragg soliton near the PBG structure, thepresent model (BG-CQ) has been analyzed in the temporal domain.

Under the influence of quintic nonlinearity, the governing NLCM equations were reduced to PNLStype equation by multiple scale analysis. Using coupled-phase amplitude method, generation of brightgrating soliton near the PBG structure in the presence of quintic nonlinear effects has also beendiscussed in detail.

The fourth chapter deals with the nonlinear pulse propagation in one-dimensional PBG structuredoped uniformly with inhomogeneously broadening two-level atoms. The pulse propagation in sucha uniformly doped PBG structure is governed by nonlinear-coupled mode Maxwell-Bloch (NLCM-MB) equations. In order to discuss the generation of SIT-Bragg solitons, the NLCM-MB equationshave been reduced to effective NLCM equations. The resulting effective NLCM equations describethe pulse propagation through a uniformly doped PBG structure. In order to discuss the SIT solitonsnear the PBG edges, the effective NLCM equations are further reduced to an effective nonlinearSchrödinger type equation.

In the fifth chapter, the results and discussions are presented. The scope for future work has also beensuggested in detail.

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Experimental study of laser driven pulsed electron and keV x-raygeneration and its applications

ANAND MOORTILaser Plasma Division,

Raja Ramanna Centre for Advanced Technology, Indore - 452013email: [email protected]

Generation of high brightness x-ray pulses of tens of picosecond to several nanosecond durationhas been of considerable interest for a variety of scientific and technological applications. Although,synchrotron radiation sources offer many interesting features, they are large, complex and expensivedevices, which are often set up as central facilities. This has motivated the development of alternativeless expensive compact laboratory x-ray sources for specific applications which do not need all thedistinctive features of the synchrotron radiation sources. In this regard, several other x-ray sourcesviz. laser-produced plasmas, different pinch plasma sources (various types of Z-pinch, plasmafocus, X-pinch etc.) have been developed. At the same time, x-ray generation by electronbombardment of solid targets has been the most important practical method of generating x-rayssince their discovery. Conventional x-ray diode with thermionic emission cathode has severallimitations, in particular its inability to generate nanosecond duration x-ray pulses. Therefore, useof various other types of cathodes viz. field-emission cathodes, explosive-emission plasma cathodes,and laser driven cathodes, have attracted considerable attention in the recent years for developmentof compact, cheap, laboratory vacuum diode based multi-keV flash x-rays systems. In particular,vacuum diode x-ray sources using laser based electron sources are very attractive due to theirsuitability for pump and probe type experiments as the x-ray pulse can be temporally synchronizedwith an external event involving laser irradiation. Laser based cathodes include laser driven photo-cathodes, laser-produced plasma, and laser-induced electron emission from ferroelectric materials.Among these, ferroelectric materials are relatively new type of cathodes. They have manyadvantageous features, such as : ease of fabrication, room temperature and high rep rate operation,resistance to atmospheric contamination, and provide a high current density (³ 100 A/cm2).

In the present thesis work, we have experimentally studied the x-ray emission characteristics of avacuum diode x-ray source with laser-produced plasma as the cathode from the point of view ofsetting up a cheap, compact, multi-keV, nanosecond laboratory x-ray source. Adequacy of this x-ray source for x-ray radiography application has been demonstrated. Next, a novel extension of theabove technique was carried out for simultaneous generation of twin x-ray sources (by using twoanodes) for potential application in stereo-radiography. Further, the effect of laser pulse durationon the discharge characteristics has also been studied. Cathode plasma jet pinching was observedwhen multi-picosecond duration laser pulses were used to produce plasma on the cathode. In additionto the intense K-shell x-ray emission from the titanium anode due to bombardment of electronsextracted from the cathode plasma, evidence of much harder component (hn > 100 keV) was alsoseen in the discharge. Next, high-current-density pulsed electron emission from lead zirconiumtitanate (PZT) ferroelectric ceramic disc was studied to understand the physical mechanismsinvolved. Electron emission was studied in two different modes: 1) by laser pulse irradiation of thePZT disc surface, and 2) by applying a high-voltage pulse across the PZT disc. The former methodis referred to as laser-induced electron emission (LIEE) and the latter one as field-excited electronemission (FEEE).

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The Influence of Microenvironments on Photoinduced ElectronTransfer and Excited State Proton Transfer Processes.

TUSHAR KANTI MUKHERJEEDepartment of Chemistry,

Indian Institute of Technology Bombay, Powai, Mumbai-400076email: [email protected]

The ultrafast photoinduced electron transfer (PET) from chlorin p6 to methyl viologen and from

amines to core-modified cationic porphyrins has been found to be slowed down in micelles.The solvent – assisted excited-state proton transfer (ESPT) in 2-(2’-pyridyl)benzimidazole isfound to be promoted at negatively charged interfaces of micelles, reverse micelles, nafion filmand in polyacrylamide hydrogels. This opens up the possibility of using this fluorophore inconfocal microscopy and fluorescence sensing.

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Development and Characterization of Diode-PumpedSolid-State Lasers

PRANAB K. MUKHOPADHYAYSolid State Laser Division,

Raja Ramanna Centre For Advanced Technology, Indore - 452013. email: [email protected]

In the recent years, there has been considerable interest in the development of diode-pumpedsolid state (DPSS) lasers because these are not only compact and efficient but also offer betterbeam quality. Due to continued reduction in cost of commercially available diode lasers DPSSlasers are emerging as a replacement for gas-ion lasers and flash lamp pumped solid state lasers.

In this thesis we report experimental and theoretical studies on diode laser pumped solid statelasers which were operated in CW, pulsed and intracavity frequency doubled configuration.These studies culminated in the development of novel systems like dual gain CW Nd:YVO

4

laser with variable degree of polarization of the output beam and passively Q-switched mode-locked intracavity frequency doubled DPSS laser. Another important development was theintracavity frequency doubled green laser offering CW power up to 30W and optical to opticalconversion efficiency of 11% and average power of 75 W with 20% optical to optical conversionefficiency. Further, several novel experimental techniques have been developed to measureparameters like the diode beam spot-size, thermal loading at the gain medium and stimulatedemission cross-section of the gain medium. Novel experimental techniques to reduce the FWHMwidth of the intracavity frequency doubled green pulses and to improve the spatial shape of thegreen beam also have been demonstrated. Details of these systems as well as theoretical andexperimental studies carried out to optimize their performance are presented in the thesis.

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Development and Stability Study of Nonlinear MirrorMode-locked Laser

S. MUKHOPADHYAYDepartment of Physics & Meteorology,

IIT Kharagpur - 721302e-mail: [email protected]

Mode-locking of laser using second order nonlinear optical interaction, is the subject of study inthis thesis. One scheme, known as nonlinear mirror (NLM), uses a frequency doubling nonlinearcrystal (NLC) and a dichroic output coupler to provide direct amplitude modulation of intracavityradiation. The present thesis explores the saturable absorber parameter of a NLM, prediction ofsteady state pulse width, study of stability regime of NLM and uses Innovative technique forinverse saturation of laser loss to get stable, self-starting, self-sustained and power scalable cwmode-locking.

NLS-6 108

Investigation of Laser Induced Fluorescence to Study the Plant andAnimal Health

B.S. MUNDEK.K.M. College, Manwath-431 505

Dist. Parbhani (Maharashtra)email : [email protected].

Present thesis is related with the applications of lasers in biology and medicine. In the presentwork, we have used the different lasers to study the health status of the plants. Also we haverecorded the LIF and SL spectra of cancerous and adjacent normal tissues from different organsof the human body and explored the potential of lasers as a diagnostic tool for the early detectionof cancer.

NLS-6 109

Development and Characterization of a Table Top Terawatt Nd:glassLaser System and Ultrashort Pulse Diagnostics

AVNISH KUMAR SHARMALaser Plasma Division,

Raja Ramanna Centre for Advanced Technology, Indore-452 013email: [email protected]

Since the invention of laser in 1960, there has been an unending quest for achieving higher andhigher laser power for different applications. Presently, there are laser systems, which deliverlaser peak power in excess of 1015W (1PW) and operate in both the regimes of low-energyultrashort laser pulses (e.g. few10J/ sub 50 fs) and high-energy short laser pulses (e.g. few 100J/ sub-ps). Development of such ultrahigh power laser systems has opened up new regimes ofultrahigh field physics and development of compact x-ray sources, particle accelerators, fusionneutron source, inertial confinement fusion, nuclear medicine, nuclear waste disposal etc. Suchlasers are based on either chirped pulse amplification (CPA) scheme or its variant, the opticalparametric chirped pulse amplification (OPCPA) scheme to avoid non-linear optical effects andoptical damage in direct amplification of ultrashort laser pulses in mater oscillator and poweramplifier (MOPA) scheme.

The present thesis deals with design, development and characterization of a CPA based tabletop terawatt (T3) Nd:glass laser system, and development an important sub-system of an OPCPAbased high power laser system viz synchronized pump laser delivering sub-ns laser pulses.Development of such lasers and their applications, both require reliable ultrafast spatio-temporalmeasurement techniques to determine the various pulse parameters like pulse duration, pulseshape, chirp, pulse-front tilt etc. This thesis also presents several new, simple, sensitive and lowcost diagnostics for ultrashort laser pulses.

Chapter 1 of the thesis presents a review of the state-of-art ultraintense laser systems, laserpulse diagnostics and future trends in these research arenas. Chapters 2 and 3 are devoted todesign considerations of a CPA laser, development and characterization of Nd:glass based T3

laser system and highly stable regenerative amplifier respectively. The Nd:glass T3 laser systemconsists of a femtosecond oscillator followed by a Martinez pulse stretcher, pulse selector,regenerative (regen) amplifier, pulse cleaner, two power amplifiers, beams expanders and vacuumspatial cum image relay system and a Treacy pulse compressor. Except for the oscillator, whichis a commercial system, all other subsystems are built in-house. Due to the electromagneticinterference noise arising from switching of high voltages applied to several electro-optics unitsincorporated in the system, it was not possible to operate the laser reliably, especially the regenamplifier. For this purpose, specially designed electromagnetic interference shields have beenmade and incorporated in each electro-optic unit of the laser system. A safety interlock to avoidany damage to optical components, due to any accidental injection of un-stretched laser pulsesinto regen amplifier, has also been incorporated. Highly stable operation of the regen amplifier

NLS-6 110

via interplay between the gain and distributed losses has been simulated and demonstrated. Theexperimental measurements on gain narrowing, ASE and pre-pulses have been carried out.

Chapter 4 deals with the design, development and use of second harmonic generation basedsingle shot and multiple shot autocorrelators for measurement of pulse duration and pulse-fronttilt (PFT) without ambiguity of its sign. The origin of PFT in an optical element has beentheoretically studied and general expressions have been derived. Since the non-linear crystalspresents several problems (e.g. requirement of phase matching) for their use in such applications,commercial light emitting diodes LEDs have been used as a quadratic detectors. These havebeen characterized for intensity dynamic range and for the effect of various parameters viz.ageing, reverse bias voltage, incident laser polarization etc. Chapter 5 discusses the experimentalresults on characterization of such LEDs for their use in parallel and cross-polarizedautocorrelation measurements.

Chapter 6 presents the design, development of a real time autocorrelator with extended temporalscan range. This autocorrelator is based on commercial LEDs and uses commercial audio speakersfor delay line. Chapter 7 presents a new, simple, and sensitive technique for detection andmeasurement of pulse parameters (like chirp and pulse asymmetry), and its practicalimplementation. This technique uses difference of normalized envelope functions of unbalancedfringe resolved interferometric autocorrelation (UFRIAC) signals. For any new technique, suchas the unbalanced fringe resolved interferometric autocorrelation envelope function difference(UFRIACED), it is essential to carry out noise analysis to ensure its usefulness in real laboratoryenvironment. Such an analysis has been carried out.

Chapter 8 presents the design and development of a new type of laser oscillator to generatesynchronizable, highly stable and tunable laser pulses of duration in the range of 800ps to 6nsfor OPCPA based high power laser system. Finally, the thesis concludes with the Chapter 9,which summarises the outcome of the research work, recommendations for further researchwork and future prospects in this area.

NLS-6 111

Analysis of Nonlinear Optical Response of Rhodopsin Proteins and itsapplication to All-Optical Computing

PARAG SHARMADepartment of Physics & Computer Science,

Dayalbagh Educational Institute (Deemed University), Agra - 282005email: [email protected]

Recent developments in nano-photonics have given impetus to synthesize novel photosensitivemolecules for all-optical information processing. The possibility of tailoring the nonlinear opticalresponse at the molecular level coupled with advantages of small size and weight and lowpropagation delay and power dissipation make interesting prospects for optimized deviceapplications.

The naturally occurring photosensitive biological molecules optimized over centuries of evolutionoffer exciting possibilities for device applications. There has been tremendous research interestin investigating biomolecules especially the photochromic retinal protein bacteriorhodopsin(bR) contained in the purple membrane fragments of Halobacterium halobium, for bio-molecularphotonic applications. Halobacterium halobium has at least three more retinal pigments, i.e.halorhodopsin (hR), sensory rhodopsin (sR) and phoborhodopsin (pR), also called sRII. Morerecently, the photoreceptor pharaonis phoborhodopsin (ppR) has received much attention dueto its stability and its recent structure elucidation. Proteorhodopsin (pR) is a recently identifiedfamily of proteins analogous to bacteriorhodopsin and seem to be spectrally tuned to differenthabitats – absorbing light at different wavelengths in accordance with light available in theenvironment.

The excitation of these rhodopsins protein molecules by green laser light induces their photocyclei.e. formation of different photo-intermediates having different peak absorption wavelengths.The population of different intermediate states depends upon the intensity of pumping light.Thus, the absorption coefficient at different wavelengths is also a function of pump intensityand the transmission of weak probe beam corresponding to peak absorption wavelength ofdifferent photo-intermediates can be controlled by varying the pump beam intensity. Thesenonlinear transmission characteristics of these rhodopsins proteins have been theoreticallyanalyzed in pump-probe geometry considering cw and pulsed pump excitation, respectively.Transmission characteristics have been simulated considering the typical photocycle of threeproteins (bR, ppR and pR) using the rate equation approach.

The spectral and kinetic properties of these rhodopsins proteins can be changed by variousphysical, chemical and genetic engineering techniques. The effect of kinetic and spectralparameters and normalized small signal absorption coefficient has also been studied ontransmission characteristics. There is an optimum value of concentration of protein moleculesat which maximum modulation of the probe beam can be achieved. The modulation of probebeam can also be increased by increasing the absorption cross-section of initial state and probed

NLS-6 112

state at pump and probe wavelengths, respectively, and decreasing the absorption cross-sectionof initial state at probe wavelength and rate constant of the probed state.

Nonlinear transmission characteristics of these rhodopsins proteins have also been used to designall-optical spatial light modulators (SLMs), parallel logic gates, switches and a multiplexerwhich are the building blocks of information processing system. These devices have also beenoptimized in terms of different parameters such as; concentration of protein molecules, pumpintensity, pump pulse width, absorption cross-sections and lifetimes of different intermediatesof protein molecule.

Theoretical simulations of transmission characteristics of bR and ppR are in good agreementwith experimental studies performed in collaboration with Prof. D. Mathur, Tata Institute ofFundamental Research, Mumbai and Prof. N. Kamo, Hokkaido University, Japan. Our resultsshow that the relative phase difference between the switched probe beam and the pulsed pumpbeam and profile of switched probe beam are sensitive to the frequency of the pump pulses andintensity and wavelength of probe beam.

At typical parameters, wild-type (WT) ppR based computing devices can be realized atconsiderably lower pump powers than WT-bR. The switching contrast for probe beamtransmission is low for pR in comparison to bR and ppR. The analysis provides the basicunderstanding of nonlinear absorption processes in rhodopsins proteins that exhibit a complexphotocycle. The proposed all-optical computing devices would also be useful due to simple lowpower and parallel operation, small linear absorption coefficient, flexibility in design andenvironmentally safe technology. These molecular devices can be operated at very low power incomparison to organic dye based devices.

NLS-6 113

Optical Imaging and control of convection around a KDP crystalgrowing from its aqueous solution

ATUL SRIVASTAVADepartment of Mechanical Engineering,

IIT Kanpur-208 016email : [email protected]

A crystal growing from its aqueous solution creates a three-dimensional solute distribution inits vicinity by withdrawing solute from the bulk of the solution rich in concentration, causingthe solute concentration to decline in the neighboring solution. The solutal concentrationgradients, and hence the gradients in the density of the solution are responsible for the evolutionof buoyancy-driven convection currents in the growth chamber in free convection regime1.However, measurement of convection patterns has posed certain difficulties. In this context,laser measurement techniques have become popular, though primarily as a flow visualizationtool. The nature of convection and its relationship to solute distribution, crystal growth ratesand quality remains to be fully established. For this reason, the dependence of the convectionpatterns on the process parameters has been explored in the present study. The process parametersvaried are cooling rate of the solution and the rotation rate of the growing crystal. Crystal rotationis seen in this work as a means of diminishing the impact of buoyancy. It can also be an alternativeto growth under microgravity conditions. The crystal size plays an influential role in determiningthe relative importance of buoyancy and rotation. An independent study of crystal size has alsobeen presented. Projection data recorded in the form of two-dimensional schlieren images hasbeen employed to reconstruct the three-dimensional concentration field around the growingcrystal with the help of tomography algorithms2.

Mapping of convection patterns as well as the concentration field in the growth chamber isrequired to understand the mechanism of crystal growth and to establish appropriate conditionsfor growing large defect-free crystals. Unlike growth from melt and vapor, growth of a crystalfrom an aqueous solution is particularly amenable to optical visualization since the solution istransparent. It is possible to generate images of the convective field by exploiting changes in therefractive index that accompany changes in the density of the medium. The visualization techniqueis thus useful for on-line monitoring of the growth process.

Optical techniques are ideal for mapping the properties of the solution during a crystal growthexperiment because they are non-intrusive and inertia-free. In addition, the images recorded canbe interpreted as path integrals in the direction of line-of-sight. Local properties can besubsequently reconstructed by using principles of tomography. In the present study, imagesfrom three refractive index-based methods namely, interferometry, schlieren and shadowgraphare presented. The suitability of these measurement techniques to image, analyze and interpretthe convective field around a growing crystal is explored. The crystal material chosen forexperiments is potassium-di-hydrogen-phosphate (KDP).

NLS-6 114

A direct comparison of the refractive-index based techniques shows that interferometry is bestsuited when density gradients in the fluid medium are small. For high density gradients,shadowgraph images contain the greatest amount of information. While interferograms are easyto analyze, it is difficult to retrieve concentration data from a shadowgraph. As a balance betweenease of analysis and sensitivity to density gradients, schlieren emerges as the best option forcrystal growth applications.

On the basis of schlieren imaging, results obtained in the present work show that the growthrates are well-correlated with regions of large concentration gradients. Rotation serves to diminishconcentration gradients near the crystal by homogenizing the solution. Accordingly, the growthrate is seen to be the highest in the buoyancy-driven convection regime, while the quality of thegrown crystal is superior in the presence of rotation. The three dimensional distribution ofconcentration shows a strong correlation with the topography of the growing crystal.

References :

[1] W.R.Wilcox, ”Transport phenomena in crystal growth from solution”, Prog. Crystal Growthand Charact. Vol. 26, pp. 153-194 (1993).

[2] F. Natterer, The Mathematics of Computerized Tomography, John Wiley, New York (1986).

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List of Exhibitors at NLS-6

✦ Laser Science, Mumbai - Dr Lalit Kumar

✦ Anatech Instruements, Mumbai - Dr Sanjay Naik

✦ Simco Global Technology and Systems Ltd., New Delhi - Dr Dariyan

✦ Laser Spectra Services, Banglore - Mr N R P Kumar

✦ Specialised Instr. Marketing Co., Mumbai - Mr Sanjiv Deshpande

✦ Dynotech Inst., New Delhi - Dr Sudhir Sharma

✦ Inde Enterprises, Chandigarh - Mr Ashok Sunder

✦ Excel Technology, Mumbai - Mr P P Sohjan

✦ Jain Laser Tech., Mumbai - Dr Mahavir Jain

✦ Laser Scanning Systems Pvt Ltd., Indore - Mr Jagmohan Singh

✦ Advanced Photonics, Mumbai - Dr B M Prasad

✦ Holmarc Slides and Controls Pvt Ltd., Kochi - Mr Vinod R

✦ Newage Instr, Delhi - Mr Sameer Sarda

✦ Scientific Solutions, New Delhi - Mr D S Rawat

✦ I R Optics, Faridabad - Mr J M Bhasin

✦ Sinsil International, Vadodara - Mr K Ramesh

✦ Light Guide Optics, Indore - Mr Siddharth

✦ Khandela Electronika, Indore - Mr Dipesh Khandelwal

✦ AVJ Optics, Pune - Dr Joglekar

✦ AMIL International, Vadodara - Mr Deepak Yewale

✦ Scientific Mes-Tek, Indore - Mr Yogesh Pandey

✦ Photonics Marketing, Mumbai - Mr Atulya Sahay

✦ Indo-French High Tech., Mumbai - Mr B R Sharma

NLS-6 116

NATIONAL ADVISOR Y COMMITTEE

Anil Kumar LASTEC, DelhiArora B.M. TIFR, MumbaiBaldev Raj IGCAR, KalpakkamBanerjee S. BARC, MumbaiBhandari R.K. VECC, KolkataGantayet L.M. BARC, MumbaiGirijavallabhan C. CUSAT, CochinGrover R.B. BARC/BRNS, MumbaiGupta P.D. RRCAT, IndoreKakodkar A. DAE, MumbaiKaw P.K. IPR, AhmedabadKrishnamurthy J.A.R. IRDE, DehraDunMathur D. TIFR, MumbaiNatarajan P. NCUFP, ChennaiNath A.K. RRCAT, IndoreNathan T.P.S. Univ. of HyderabadRadhakrishan P. VIT, VelloreRay A.K. BARC, MumbaiRustagi K.C. IIT, MumbaiSahni V.C. BARC/RRCAT, IndoreSimon P. Inst. of Mat. Sci, ChennaiSirohi R.S. Barkatullah Univ., BhopalSood A.K. IISc, BangaloreThareja R.K. IIT, Kanpur

NLS - 6 COMMITTEES

NLS-6 117

SYMPOSIUM ORGANISING COMMITTEE

Bhattacharya K. IACS, KolkataChandrachoodan P. BRNS, MumbaiDasgupta K. BARC, MumbaiDhanasekaran R. Anna Univ., ChennaiDhareshwar L.J. BARC, MumbaiGupta P.K. RRCAT, IndoreMago V.K. BARC, MumbaiMehendale S.C. RRCAT, IndoreNampoori V.P.N. CUSAT, KochiNatarajan V. IISc, BangaloreOak S.M. RRCAT, IndorePal S. LASTEC, DelhiPuri R.R. BARC, MumbaiRamachandran H. RRI, BangaloreRamamurthy P. NCUFP, ChennaiRao D.N. Univ. of HyderabadRavindrakumar G. TIFR, MumbaiRoy S.K. IIT, KharagpurSarkar S.K. BARC, MumbaiSen P.K. SGSITS, IndoreSingh B.P. IIT, MumbaiSuri B.M. BARC, MumbaiTata B.V.R. IGCAR, KalpakkamThyagrajan K. IIT, DelhiUmapathi S. IISc, BangaloreNundy U. (Convener) RRCAT, IndoreGanguli T. (Secretary) RRCAT, Indore

TECHNICAL COORDINA TION COMMITTEE:

S.M. Oak (Chairman) RRCAT, IndoreP.A. Naik RRCAT, IndoreDivakar Rao RRCAT, IndoreS.V. Nakhe RRCAT, IndoreS.M. Gupta RRCAT, IndoreR. Kaul RRCAT, IndoreC.P. Navathe RRCAT, IndoreS. Chatterjee RRCAT, IndoreSendhil Raja RRCAT, IndoreArup Bannerjee RRCAT, IndoreK. Dasgupta BARC, MumbaiB.M. Suri BARC, MumbaiTapas Ganguli RRCAT, Indore

NLS-6 118

LOCAL ORGANIZING COMMITTEES FOR NLS-6:

U. Nundy - Convener

Tapas Ganguli - Secretary

Milind Edlabadkar - Treasurer

I. Accommodation Committee :

Manoj Kumar ICLS CoordinatorPankaj Bhargava ICLS Co-CoordinatorP.C. Jain C&S MemberS.M. Jalali C&S MemberAjit Upadhaya LPD MemberVibhuti B Tiwari LPAD MemberVijay Shukla LPAD MemberT. Ahmad G.House Member

II. Reception & Transport Committee :

A.K. Karnal LMD&DD CoordinatorM.P. Kamath LPD Co-CoordinatorD.K. Kohli LMD&DD MemberN.S. Bannerjee CELS MemberP.K. Tripathi LPD MemberK. Muralikrishna LSED MemberSunil K Sharma SSLD MemberK.K. Dange Admin. Member

III. Food & Catering Committee :

H.S. Rawat LPAD CoordinatorG. Mundra MAGDIV Co-CoordinatorR.V. Joshi C&S MemberP. Bhatnagar CELS MemberAshutosh Sharma SSLD MemberSanjiv Tiwari LPAD MemberT. Ahmad G.House MemberSudarshan Patwa HPLOL Member

IV. Hall Arrangement Committee :

M.R. Jathar CTRMS CoordinatorK.M. Khare LBAID Member

NLS-6 119

V. Registration Committee & Help Desk :

Rama Chari LPAD CoordinatorBeena Jain LBAID Co-CoordinatorB.B. Shrivastava CELS MemberJ. Jaybalan LPAD MemberJagriti Khanwalkar SSLD MemberT. R. Sagith Kumar SSLD MemberSiddesh Arun Pai LBAID MemberN.M. Suresh Accounts MemberP. Sharma Admin MemberH.S. Hada Admin Member

VI. Publication & Printing Committee :

K.S. Bartwal LMD&DD CoordinatorRajiv Jain LSED Co-CoordinatorP. Mishra LMD&DD MemberL. Sudarsan WS-B MemberS.P. Ram LPAD MemberTapas Ganguli SSLD MemberInderjeet Singh LSED Member

VII. Cultural Committee :

Alka Ingale LPAD CoordinatorM.P. Singh LPAD Co-CoordinatorBeena Jain LBAID MemberAparna Chakraborty SSLD MemberR.K. Sharma C&S MemberAmit Saxena LMD&DD Member

VIII. Internet & E-Mail Facility :

Anil Rawat CTRMS CoordinatorAlpana Rajan CTRMS MemberT. Raghu ICLS MemberItisri Kalpana Nayak LSED Member

IX. Exhibition Committee :

J.K. Mittal LSED CoordinatorS.R. Mishra LPAD Co-CoordinatorAnil Pundalik C&S MemberK. Ranganathan SSLD MemberS.D. Singh SSLD MemberSurendra Singh LPAD MemberHarish Kumar ICLS MemberP.K. Mishra C&S Member

NLS-6 120

X. Poster Committee :

A.S. Joshi LPD CoordinatorY.B.S.R. Prasad LPD Co-CoordinatorNirmalya Ghosh LBAID MemberN.M. Shenoy LSED MemberP. Ganesh ICLS MemberR. Sunder SSLD MemberAsmita Malik LBAID MemberP.B. Kamble WSB Member

XI. Travel Cell :

P. Sharma Admin CoordinatorPravin Jain DIROFF MemberS.D. Meena DIROFF Member

XII. V olunteers :

N.K. Rai (Reception) CELSR.C. Yadav (Exhibition) C&SP.K. Bhan (Registration) C&SJagdish Keshwani (Registration) C&SS.M. Perkar (Registration) ICLSC.U. Jayakumar (Exhibition) LSEDS.M. Sharma (Reception) LMD&DDS.R. Khade (Reception) LPDAshok R Nirpharke (Registration) DIROFFB.K. Arya (Publication) LSEDSaleem Shaikh (Reception) WSBP. Cheena Rao (Reception) WSBN.D. Malviya (Hall Arrangement) CTRMSC.H. Premsingh (Catering) ICLSO. Dongre (Reception) CELSK.K. Mani (Reception) LSEDA.K. Jaiswal (Accomodation) CELSDheeraj Shukla (Catering) LSEDRiyaz Ahmad (Reception) WSBK.C. Parmar (Accomodation) CELSPrabhu U Sangale (Accomodation) ICLSH. Chitre (Hall Arrangement) CTRMSG. Khonde (Transport) AdminRamesh Moopanar (Registration) AccountsJ. Sisodiya (Secretarial help) CELSR.C. Verma (Registration) Admin

NLS-6 121

Raja Ramanna Centre for Advanced TechnologyIndore

Website: www.cat.ernet.in

LIST OF IMPOR TANT PHONE NUMBERS

Dr. V.C. Sahni, Director, RRCAT 248 8847, 248 8848

Dr. P.D. Gupta, 248 8462 (Head, Laser Plasma Division, RRCAT and President, ILA)

Mr. U. Nundy (Convener, NLS-6) 244 2403, 248 8245, 248 7317 (R)

Dr. Tapas Ganguli (Secretary, NLS-6) 248 8355, 248 8320, 248 7036 (R)

Dr. Manoj Kumar (Accomodation, NLS-6) 248 8398

Dr. Rama Chari (Registration, NLS-6) 248 8375

Mr. A.K. Karnal (Transport, NLS-6) 248 8663

Mr. D.S. Rao (Chief Admn Officer, RRCAT) 248 8817, 248 8816

Mr. P. Sharma (PRO, RRCAT) 248 8855

Guest House RRCAT 244 2373

Guard House RRCAT 248 8333

Health Centre RRCAT 248 7029, 248 7043, 248 7666

Hotel Purva 2540920, 2540856

IUC Guest House 2365246

RAILWAYS :

Enquiry 131, 132

Reservation Status 135

AIRLINES :

Indian Airlines 2621782, 2620758, 2431596

Jet Airways 2620819, 2620454

2620893, 2544590-93

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F rom T o A ir line F ligh t N u m ber

D epartu re T im e

A rr iva l T im e

D ays o f O p era tion

In d ian A ir lines

IC 134 2030 H rs 2135 H rs D a ily

Jet A irw ays 9W 382 0755 H rs 0905 H rs D a ily In d ian A ir lines

IC 8134 1735 H rs 1840 H rs 3 ,5 ,7

IN D O R E

M U M B A I

Jet A irw ays 9W 384 2045 H rs 2200 H rs D a ily Jet A irw ays 9W 3309 0825 H rs 1125 H rs D a ily * A ir D eccan D N 536 1705 H rs 1950 H rs D a ily # In d ian A ir lines

IC 133 0730 H rs 0900 H rs D a ily *

Jet A irw ays 9W 3307 2000 H rs 2200 H rs 1 ,3 ,4 ,5 ,6 ,7

IN D O R E D E L H I

In d ian A ir lines

IC 8133 2105 H rs 2230 H rs 3 ,5 ,7

In d ian A ir lines

IC 133 0730 H rs 0800 H rs D a ily IN D O R E B H O P A L

Jet A irw ays 9W 3309 0825 H rs 0910 H rs D a ily IN D O R E G W A L IO R A ir D eccan D N 536 1705 H rs 1845 H rs D a ily

In d ian A ir lines

IC 133 0540 H rs 0645 H rs D a ily

Jet A irw ays 9W 381 0610 H rs 0725 H rs D a ily Jet A irw ays 9W 383 1845 H rs 2000 H rs D a ily

M U M B A I IN D O R E

In d ian A ir lines

IC 8133 1920 H rs 2035 H rs 3 ,5 ,7

Jet A irw ays 9W 3309 0555 H rs 0755 H rs D a ily A ir D eccan D N 535 1355 H rs 1645 H rs D a ily # In d ian A ir lines

IC 8134 1530 H rs 1705 H rs 3 ,5 ,7

Jet A irw ays 9W 3307 1635 H rs 1930 H rs 1 ,3 ,4 ,5 ,6 ,7 *

D E L H I IN D O R E

In d ian A ir lines

IC 7134 1715 H rs 1945 H rs D a ily *

In d ian A ir lines

IC 134 1915 H rs 1945 H rs D a ily B H O P A L IN D O R E

Jet A irw ays 9W 3307 1845 H rs 1930 H rs 1 ,3 ,4 ,5 ,6 ,7 G W A L IO R IN D O R E A ir D eccan D N 535 1510 H rs 1645 H rs D a ily * v ia B H O P A L # v ia G W A L IO R

AIR TIME TABLEUpdated on 12 June 2006, currently valid

1-Monday …………………7-Sunday

Note: Readers are requested to verify the Air timing from Airport before undertaking their journey.

NLS-6 123

No. Dep. Days Train Name (Broad Gauge) Number Arrival Days

9305 23:00 2,4,6 Indore-Howrah-Indore Kshipra Exp 9306 03:30 1,3,6

2962 15:50 Daily Indore-Mumbai Avantika Exp 2961 09:20 Daily

2415 16:20 Daily Indore Nizamuddin Intercity Exp 2416 11:55 Daily

8233 17:00 Daily Indore Bilaspur Indore Narmada Exp 8234 10:50 Daily

2919 14:00 Daily Indore-Jammutavi Malwa Exp 2920 13:10 Daily

9323 07:15 Daily Indore-Bhopal Indore Intercity Exp 9324 21:25 Daily

9310 22:00 Daily Indore Gandhinagar Indore Shanti Exp 9309 06:30 Daily

9319 20:45 1,3,5 Indore-Bhind-Indore Exp 9320 07:30 1,3,5

4317 16:05 6,7 Indore-Dehradun-Indore Exp 4318 07:30 6,7

2973 22:30 1,6 Indore-Jaipur-Indore Exp 2974 07:00 1,6

288 08:00 Daily Indore-Nagada-Indore Passenger 287 19:25 Daily

289 23:30 Daily Indore-Bhopal-Indore Passenger 290 05:20 Daily

6325 15:10 1 Indore-Trivandrum-Indore Ahilya Exp. 6326 05:00 1

107 18:00 Daily Indore-Ujjain-Indore Passenger 106 09:00 Daily

9312 13:40 1,4 Indore-Pune-Indore Exp 9311 10:30 3,6

9313 12:30 3 Indore-Rajendranagar Indore Exp. 9314 15:00 6

9321 12:30 6 Indore-Rajendranagar (Patna) Indore 9322 15:00 2

2913 20:45 7 Indore-Nagpur-Indore Trishatabdi Exp 2914 07:00 2

279 06:00 Daily Indore-Maksi-Indore Passenger 280 11:20 Daily

285 13:20 Daily Indore-Chhindwara Penchvali Exp. 286 14:20 Daily

2923 21:35 3 Indore-Nagpur-Indore Exp 2924 05:50 5

RAILWAY TIME TABLEWESTERN RAILWAY

TRAINS LEAVING INDORE TRAINS ARRIVING INDORE

1.: Monday, 2.:Tuesday…………………………………..7.:Sunday

Note: Readers are requested to verify the train timing from Railway Station before undertaking their journey.

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