NOVEL MATERIALS FOR FUTURE; NANOCOMPOSITES FOR PHOTONICS

SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH19, UNIVERSITY ROAD, DELHI-110 007

Email : sridlhi@vsnl.com Website : www.shriraminstitute.org

Presented by :Dr. R.K. KHANDAL

Outline of the Presentation

Photons & PhotonicsDefinition

Properties

Interaction of electromagnetic radiation with matter

Need for novel materials

Evolution of optical system technologies

Materials

ApplicationsComposites for Nanophotonics

Confinement of Energy

PHOTONICS

Photons

Interactions of electromagnetic radiation with matter

Photonics

Optical phenomena

Photons: Relevance

What are photons ? Omnipresent source of vital energy

What is the relevance?

Carrier of InformationWhat is energy ?

Using the Vital Energy to get Vital Information

Photons: Basic properties

Zero electric charge & no rest massEnergy & momentumDual nature (wave & particle)

Not be destroyed / & created

Produce effects, i.e. photo-electric, compton & ion-pair

Photons have:

Photons can:

Zillions of photons in an ordinary light beam

Interactions of photons with matter (materials) is the key!

Interactions of electromagnetic radiations with matter

Matrix

e-

Photoelectric Effect

Matrix

e-

Compton Scattering

Matrix

Pair Production

e-

e+

Transfer of all energy of photon to electron

Elastic collision of photons with atomic electrons

Ionization Momentum to target electron

K.E of a photon

2 new particles with K.E

Formation of electron & positron

Photodiodes, sensors photomultipliers, Image transistors

Radiobiology, Radiation therapy Stellar explosions

7

Metals with small Atomic No. Photoelectric effect CE observed at energy Energy range for CE Energy required for PP

Metals with higher Atomic No. Photoelectric effect CE observed at energy Energy range for CE Energy required for PP

Photoelectric effect (PE) Dominant

Pair production

(PP) Dominant

Compton effect (CE) Dominant

0.10.01 10 100

Ato

mic

No.

of

the

targ

et

0

20

40

60

80

100

120

1Photon incident energy (MeV)

Interaction of Electromagnetic Radiation with Matter

Effect of penetration depth on absorption of photons

D = 1/ D = Mean penetration depth = absorption coefficient

Majority photons will be absorbed / scattered before reaching D

Many will penetrate farther than D

Data are for D = 2

Majority of photons donot penetrate upto DTangent at x = 2 extends to intersect the zero transmission

axis at x = 4 i.e. at a depth of (x + D)27Intensity falls to 0.37(36.8%) at x = 2

Thickness extends to 5 x DExponential

absorption of photons by

matter

Development of materials by maneuvering penetration

Interaction of electromagnetic radiation with matter: Linear Optical Phenomena

Refractive Index (R.I.)

Dispersion (Abbe Number)

During interaction with light, the refractive index & other properties remain constant throughout the medium

Linear optics is a material & energy dependent property

Devices: Lenses Filters Coatings

Low HighMid

1

2

i

r

= sin i sin r

<1.5 1.5-1.6 >1.6

PC,Glass

PA, Glass

Thiourethanes, Glass

30- 60 Glass, Plastics

Difference frequency mixing (DFM)Mixing of different wave frequencies to form a coherent beam (e.g. LiNbO3, BaBO3, Poly (p-phenylene vinylene)

Four wave mixing (FWM)Channel spacing can be achieved (e.g. LiNbO3,

BaBO3, Poly (p-phenylene vinylene)

Behavior of light in nonlinear media in which the dielectric polarization P responds nonlinearly to the electric field E of the light

Change in refractive index (Δn) directs light to travel in required directions All are essential for fiber optics, optical switches, waveguides Devices based on above phenomena have the capability to switch speeds

from 1 ns to less than 1 ps Materials with both high non-linearity and low loss are required

Transmission

Generation

Modulation

Cross-phase modulation (XPM)Technique for adding information to a light stream by phase modification of coherent optical beam (e.g. LiNbO3, BaBO3, Poly (p-phenylene vinylene)

Interaction of electromagnetic radiation with matter: Non-linear Optical Phenomena

Waste Disposal (Pharma) : Energy - Efficient Technology

Plasma gasification technology eliminates the need for landfills

Pharma waste

Plasma Thermal Destruction &

Recovery

Syngas Vitrified products

Recovered metals

Electricity

Steam

Liquid fuels

Concrete aggregates

Construction

Tiles

Metal

Waste Disposal (Textiles) : Waste - to - Wealth Technology

Value-added product from textile sludge: Bricks

Cost-benefits to textile & construction industries

Textile sludge

Construction Industry

Efficient management

Useful by-product

Economic benefits

PhotonicsPharma waste

Plasma Thermal destruction &

recovery

Syngas Vitrified products

Recovered metals

Electricity

Steam

Liquid fuels

Natural gas offset

Concrete aggregates

Roadbed/fill

Construction

Tiles

Metal

Photonics

Detection

Transmission

Generation

Amplification

Semiconductors, LED,s -OLED,s, Lasers, Super luminescent diodes, Cathode ray tube, Fluorescent lamps

Glass fiber, Optical fiber, Photonic crystals, Photonic crystal fibers, Meta materials

Optical amplifier: Doped fiber amplifier Semiconductors

Raman Amplifier Quantum dot

Photo Thermal

Chemical Photoelectron

Modulation

Optical modulator Electro absorption modulator On-off key formats

All devices would need materials

Components Dimensions

Technology

Components

Materials

Alignment

Propagation

Device size

Evolution of optical systems technology

Ist Generation

ConventionalOpticsMirrors, prisms,lenses, gas lasers

Glass

Necessary

Beam

1 m2

IInd Generation

Micro-Optics

LED, LD, tinylenses, optical fibersGlass & polymers

Necessary (hard)

Waveguides

10 cm2

IIIrd Generation

Integratedphotonics

Monomode channel

waveguides,

LD

Composites

Unnecessary

Waveguides

10 cm2

Development of new materials leads to new devices & vice-versa

Electronic signal

Light signal

Processing of light

Light signal

OPTICAL-ELECTRONIC-OPTICAL

More signal losses

Light signal

Light signal

OPTICAL-OPTICAL

Less signal lossesFast speed

Detection

Detection

Present focus is more towards optical (OO) conversion of light

Current telecommunication systems combine both electronic & optical data transmission; emphasis is to move towards all optical networks due to increased bandwidth

C H 3

H 3 C ON O 2

N ( C H 3 ) 2

N +C H 3

H 3 C S O 4-

N

N

C H

C N

C N

S O 3-H 3 C

N ( C H 3 ) 2

N +C H 3

Materials for non-linear optics

3 methyl-4methoxy-4-nitrostilbene

4’-dimethylamino-N methyl-4-stilbazolium methyl sulfate

3-(1,1-dicyano ethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole

4’-dimethylamino-N methyl-4-stilbazolium tosylate

Synthesis of conventional organic optical materials is cumbersome & expensive; incorporation into optical devices is problematic

Need for alternative materials, such as nanocomposites, exists!

NH4H2PO4 Ammonium dihydrogen phosphate

Ba(BO3)2.nH2O Barium metaborate

KH2PO4 Potassium dihydrogen phosphate

LiNbO3 Lithium niobate

Incorporation of inorganic optical materials in polymers would lead to enhanced properties of nanocomposites

Materials for non-linear optics

Approaches

Semiconductor Optical Amplifiers (SOA)

Manufacturing photonic band gap structures with non-linear materials

Enhancement of non-resonant optical non-linearity using local-fields effects

Developing new crystalline & polymeric materials with high optical non-linearity

InP is used; expensive; coupling problems

Yet to build capabilities

Enhancement factors of only 10 times has been achieved so far

PTS & Polyacetylene LiNbO3 - Promising materials; expensive & difficult to process

Status

Desired Properties for Photonic Applications

Low optical loss due to absorption or scattering Linear index of refraction Large difference in refractive index High non-linearity & processability Physical & Chemical compatibility Low cost of manufacturing

Extremely difficult to find a pure material meeting he above criteria

Nanocomposites are promising materials for achieving desire properties

NANOCOMPOSITES PHOTONICS

Dimensions & confinement

Materials

Designing Composites

Fabrication

Types

Metamaterials

Applications of Photonics Nanocomposites

LEDFiber Optics

PhotovoltaicsOptical Amplifiers

Optical Switches

Three areas of Nanophotonics

Photonic crystals

Metamaterials

Confined semi-conductors

Photonic crystals & confined semi-conductors form the basis of nanophotonic composites

Dimensionality of Photonic Materials

One dimension Two dimensions Three dimensions

Flow of electromagnetic waves can be controlled by periodic variation of refractive index & dielectric constant

Designing & tailoring the key properties of polymeric materials is important for technological advancements

Refractive Indices of Materials

High refractive index materials are preferred materials

Inorganic materials: Brittle and difficult to process

Polymers: Desired for better physical properties

Inorganic nano-particles: Improvement in R.I. of polymers

Ge (633 nm) 5.5

Si (633 nm) 3.8

Air 1

Polysulfone (589 nm) 1.63

Polystyrene (589 nm) 1.59

Polypropylene (589 nm) 1.51

TiO2 (589 nm) 2.34

ZnS (589 nm) 2.43

CdS (589 nm) 2.50

Confinement- Energy vs Size

1 2 3 4 5 6 7 8 9 10

Size (nm)

En

erg

y

Energy gap shifts as a function of size (quantum confinement) Band gap energy size Energy of the emitted light size By careful control of size, fine tuning of optical & electronic

properties are possible Quantum confinement effects of semiconductor materials is

being exploited in the areas of catalysis & photonics

3 . 1 4

3 . 2 93 . 2 8

3 . 2 1

3 . 1 2

3 . 1 4

3 . 1 6

3 . 1 8

3 . 2 0

3 . 2 2

3 . 2 4

3 . 2 6

3 . 2 8

3 . 3 0

5 1 0 1 5 2 0

P a r t i c l e s i z e ( n m )

Ba

nd

ga

p e

ne

rg

y(e

V)

Size Vs Energy of TiO2 nanoparticles

Effect of particle size on the band gap energy of TiO2 finds applications in optical devices & catalysis

Ways Of Confinement

Confinement of Photon Confinement of Electron

Quantum well

Quantum wire

Quantum dot

Optical planar waveguide

Optical fiber

Microsphere Optical cavity

Application: Telecommunications Application: Semiconductor devices

Challenges-Synthesis -Specialized conditions-Commercial viability

Confinement of matter is the most viable option having wide applications !

Polymers are the only materials which confines radiation, matter & process at the nanoscale.

Criteria RequirementA Confinement

of radiation at nanoscale

- Quantum dots

- Quantum wells

- Quantum wire

B - Nanosized particles

- Established Methods (Physical & chemical)

- Wide Option of material (Inorganic & organic)

- Commercial products (Sunscreen lotions, filters) are available

C- Energy distribution (Photonic band gap)

- Nanofabrication- Intergrated Circuits

- Sensors & actuators

Status- Ongoing Research

- Large scale manufacturing

Confinement of matter at nanoscale

Confinement of processes at nanoscale

Confinement at Nanoscale

Defining Nanocomposites

Dispersed phase

Continuous phase

Quantum dots

<10 nm

Nanoparticles

~ 10-50 nm

Acts as a scattering medium through which light transmission can be manipulated to produce various photonic functions

Comprising of quantum dots & nanoparticles dispersed in a suitable polymer are novel materials for photonic applications

Bulk properties of the material, such as R.I. can be modulated Tailor making of optical & electronic properties can be achieved

by the appropriate combination of particle size & type of material

Solid Waste Disposal : Scale of Eco-friendliness

Value addition

Reuse

Prolonging life-cycle

Regeneration

Modifications

Cradle - to - Grave utility

Land- filling

Getting Rid-off

Recycling

FuelMinimum effort & best useE

co

-fr i

en

dli n

es

s

Nothing is a waste means complete eco-friendliness

Scale of Eco-friendly practices of the waste disposal :

Utility-centric Safety-driven Regeneration-specific

Disposal-centric practices are non eco-friendly

Drilling waste

Petroleum SludgeElectro-kinetic transformation

Bio-treatment Compost material

Value-addition

Application of electro-kinetics to petroleum sludge increases hydrocarbon recovery Economic benefit

Oil contaminated soil

Petroleum WasteRecycling of H/C

residue

Cost-effective

Porous ceramic articles

Waste Disposal (Petroleum) : Eco-friendly Practices

Nanocomposites

Dispersed phase

Continuous phase

Particle size < λlight

NANOCOMPOSITES

Particle size > λlight

Less light scattering

E.g. Waveguides

More light scattering

E.g. Laser paints

The optical interactions within & among the particles can be controlled to derive a specific photonic response or multifunctionality

Each particle performs specific photonic or opto-electronic function

Preparation of Photonic Nanocomposites

Incorporation

Liquids

Vapor deposition

Solids Glasses Polymers

Ion-implantation

Homogeneous films

Quantum dots

Bulk

Sound energy, Light energyElectrical energy, Thermal energyChemical energyMagnetic energy

Top down & bottom up approaches are commonly used to prepare quantum dots of varying sizes

Designing Composites: Basic Principles

Periodic arrangement of R.I. variation controls movement of photons New energy levels within the band gaps can be created by breaking the

periodicity of the photonic material by enlarging, reducing or removing voids; the desired change in refractive index can be achieved by modifying the voids

Wavelength selective structures can be formed by careful selection of symmetry & spacing

Modification of light propagation takes place through enlarging, reducing or removing voids; optical cross-connects, switches & waveguides

Photonic band gap: Restricts transmission of light to defined set of bands

Voids

Enlarged voids Reduced voids Voids removal

Matrix

OO

O

*

O

O O *

Polycarbonate APC

Amorphous

Tg = 183oC

R. I. =1.54

Criteria for an EO-polymer to be used in tuneable nanophotonic devices: It has to form low loss (low absorption & low scattering) film

Tg should be >140oC

High EO-coefficient to allow a strong variation of the transmission characteristics of the photonic structure

High concentration (20 wt. %) NLO-chromophore

Fabrication of a Photonic Nanocomposite System-1

Fabrication of Photonic Nanocomposite System-2

Modification of light propagation takes place through enlarging, reducing or removing voids; optical cross-connects, switches & waveguides

Addition of monomer

PolymerizationRemoval of

colloid spheres

FCC single crystal Partial fusion of colloids

Dedoping of polythiophene

n1 = 2.9 n2 = 1

Chemical bonding to surface

Fabrication of a Photonic Nanocomposite System-3

Surfactants

Nanoparticles

Expensive & specialized equipment not required Chemical bonding provides stability & robustness Easily implemented

Inorganic materials

Surface Functionalization

Dispersion

FilmsProcessing

Cool (-20°C)

Fabrication of Photonic Nanocomposite System-4

Heated (60 °-280°C/ 48 hrs)

Mg powder (0.05-2 mol)

End capping (phenyl lithium)

SiCl4 (0.05-0.2 mol) Dropwise addition

Dropwise addition

Quenched (dil. Protic acid)

Stirring/ 48 hrs

Extract/precipitation/drying

Dispersion in PMMA Film Casting

Mixture

Fabrication of a Photonic Nanocomposite System-5

Paste

Nanopigment (TiO2, ZnO)

Siloxane

Liquid paraffin

Anti-sun protection milk

Stirring/40ºC

Milling

Filler (SiO2, B3N, PMMA powder)

Oil in water emulsion

Water-Glycerol +propyl p-hydroxybenzoate

Stirring/80ºC

Two Dimensional Polymeric Photonic Band Gap

P2VP + PI + Polystyrene

Periodic dielectric structure (waveguide)

CdSe Crystallites (SM- trioctylphosphine oxide)

Block co-polymer

Roll cast

Mixed

120oC & vacuumAnnealed

Fabrication of a Photonic Nanocomposite System-6

Metamaterials

=µrr

Metamaterials are engineered to have EM responses which are impossible in naturally occurring materials

1

2

1

2

+ve R.I.

-ve R.I.

Refractive Index

=µrr

µr: Permeability to magnetic fieldr: Permeability to electric field

• µr, r= -ve

• Induced phenomena

µr, r= +veNatural phenomena

Metamaterials

Kinetic stability

Metamaterials allows one to harvest properties, derived from the phase that is thermodynamically not stable.

Thermodynamically unstable

Thermodynamically metastable

Thermodynamically stable

Too slowmetamaterials

Nanocomposite metamaterials

SiO2/V2O5

Interdispersed polymer with glass phase

Insoluble once formed

PPV precursor

Sol-gel

Hydrolyze

PPV-polymer with SiO2 network

PPV-glass composite exhibits high optical quality compared to pure PPV

Used in holographic gratings to filter out light of 50 pm bandwidth21

SRI’s EXPERIENCE

SRI’s Experience

SRI has experience in

High, mid and low refractive index materials

Nanocomposites for optical applications

Modification of low refractive index materials

47474747

Refractive index increases with increase in percentage of metal salt.

1.41

1.42

1.43

1.44

1.45

1.46

1.47

1.48

0 5 10 15 20 25 30Metal salt (% by wt)

Ref

ract

ive

Ind

ex

Barium Hydroxide Lead Monoxide Lanthanum Oxide

Effect of dispersion of metal salts on the refractive index of acrylic acid

48484848484848

Modification of low refractive index materials

The refractive index of low refractive index materials increases from 1.49 to 1.66

1 . 4 1

1 . 4 7

1 . 5 3

1 . 5 9

1 . 6 5

1 . 7 1

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

% o f a d d i t i v e

Ref

ract

ive

ind

ex

494949494949

Effect of metal on refractive index

In-situ formation of nanoparticles of TiThe refractive index of the polymer increases

from 1.45 to 1.53

1.44

1.46

1.48

1.5

1.52

1.54

0 2 4 6

% Ti

Re

fra

cti

ve

Ind

ex

0 . 0 0

0 . 5 0

1 . 0 0

1 . 5 0

2 . 0 0

2 . 5 0

3 . 0 0

3 . 5 0

4 . 0 0

2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0W a v e l e n g t h

Ab

so

rba

nc

e

M G A

B C

Semiconductors are used to prepare nanocomposites with enhanced photocatalytic activity

Dye

Nanocomposites & dye degradation

Nanocomposites lead to complete degradation of dyeUseful for the treatment of dye effluents

91.29 92.30 94.49

37.29

86.61 87.19

0

20

40

60

80

100

A B C

Deg

rad

ati

on

rate

(%)

Nano

Normal

Nanocomposites for dye degradation

Dye solution

Nanocomposite

Dye removal

Swelled nanocomposite after uptake of dye

Dye removal from effluent

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