Management of femtosecond laser pulse--Generation, synchronization, phase control and

amplification

Zhiyi Wei

Institute of Physics Chinese Academy of Sciences

Beijing 100080, China

Asian Summer School on Laser Plasma Acceleration and RadiationsAugust 7-11, 2006 Beijing

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OutlineFemtosecond generationSynchronization Carrier-envelope phase controlAmplification Route toward attosecond worldSummary

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2.3 fs

Toward Monocycles pulse (

4

How to get very short pulse--- Advanced mode locking techniques

SBR as cavity mirror

Modulator always on

Push or tap mirror

Activity:Self startingModulatorNon self startingStarting:

PassiveActivePassiveType:

< 20 fs, > 40 nm< 100 fs< 10 fs, >100 nmParameters

Saturable braggreflectors (SBR)

Active mode locking by AOM

Kerr Lens Mode Locking

Mechanism:

Large bandwidth: with Fourier Transform limit: ∆ν ∆τ < 0.314laser medium should has a wider gain band. Dye, Ti:sapphire.

Dispersion compensation: consider high order dispersion. the large bandwidth, the difficult for compensation

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Kerr Lens Mode-locking laser

D. E. Spence, P. N. Kean, W. Sibbett, Opt. Lett. 16, 42, 1991

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Dispersion control in Ti:sapphire laser

Jianping Zhou et al, Opt Lett, Vol. 19, 1149( 1194)

8.5fs

Lin Xu et al, Opt Lett, Vol. 21, 1259(1996)controlled by prism pair controlled by chirped mirrors

Thin crystal and accurate dispersion compensation result the very short pulse.

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What is chirped mirrorthe perfect source for negative GDD

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8Size:600mm×200mm×150mm

Prism controlled Ti:sapphire laserPrism controlled Ti:sapphire laserStability 1WPulse duration 15～30fsPeak Power ~1MWTunable range 760nm~850nmRepetition rate 50～100MHz

600mm

200mm

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Pulse duration and stabilityPulse duration and stability

-40 -20 0 20 400

1

2

3

4

5

6

7

8

Ultralasers

Inte

nsity

Time delay (fs)0 2 4 6 8 10 12

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Average power of fs Ti:sapphire laser

Pow

er(a

.u)

Running Time (hour)

10

OC T=10%

f=10 cm M1 M2Ti:sa

M3

5W 532nm Millennia

M1-M3: Chirped mirrors, F≈ 160 MHz

Chirped mirror Ti:sapphire laser

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Dispersion of Ti:S crystal and chirped mirror

0.6 0.7 0.8 0.9 1.0-75

-50

-25

0

25

50

75

100

Dis

pers

ion

of T

i:sap

phire

(1m

m)

wavelength /µm

GDD, fs2

TOD, fs3

FOD, fs4

Ti:sapphire crystal Chirped mirror

650 700 750 800 850 900 950 10001050-200

-150

-100

-50

0

50

100

Dis

pers

ion

/fs2

wavelength /nm

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Refractive index and dispersion of air

0.5 0.6 0.7 0.8 0.9 1.0

1.000275

1.000276

1.000277

1.000278

1.000279

Ref

ract

ive

inde

x of

air

wavelength /µm0.6 0.7 0.8 0.9 1.00

5

10

15

20

25

30

Dis

pers

ion

of a

ir

wavelength /µm

GDD, fs2

TOD, fs3

FOD, fs4

Dispersion of 1m air

The dispersion of air is 21.3 fs2 per 1meter at wavelength of 800nm, it enables us to accurately adjust dispersion by air

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Spectra with SPM effect

500 600 700 800 900 1000 11000.0

0.2

0.4

0.6

0.8

1.0

x=0.3 mm

1064 nm

Inte

nsity

wavelength /nm

532 nm x=0.1

x=0.2

0 100 200 300 400 500 600 700 8000

100

200

300

400

500

600

Spo

t siz

e /µ

m

Z /mm

f = Infty f = 30cm f = 20cm

F M1 M2X

M3 OC

We calculate the waist size inside the Ti:Sa crystal is 10.9 µm, Moving M2 will lead to the change of SPM

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Optimized ultrabroaden spectrum

500 600 700 800 900 1000 11000.0

0.2

0.4

0.6

0.8

1.0

Spe

ctra

l int

ensi

ty

wavelength /nm

532 nm 1064 nm

Directly output from the oscillator, covered from 550~1050nmWe generated the quasi-octave spanning spectrum with the simplest laser configuration

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Measurement of laser pulse

Sub-10fs oscillatorAg mirror

Ag mirror

Chirped mirror

Wedges

Layout Interferometer autocorrelator

autocorrelator

Chirped mirror

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Pulse duration and spectrum

One of the shortest pulse generated with the simplest laser configuration in the world. 7fs/300mW/160MHz

600 700 800 900 10000.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

(a.u

)Wavelength(nm)

-30 -20 -10 0 10 20 300

2

4

6

8

Inte

nsity

(arb

.uni

ts)

Time(fs)

7fs

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M3 M4

f M1 M2

OC

Ti:sapphire

New experiments with 5 mirrors

M1~M3: Chirped Mirrors, M4: Ag mirror

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5.2fs

2.6 2.8 3.0 3.2 3.40

2

4

6

8

Inte

nsity

(a.u

)

X Axis Title600 700 800 900 1000

0.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

(a.u

)Wavelength(nm)

New results directly from oscillator

A demonstration of quasi-5fs laser pulse only with 5 mirrors cavity. The simplest laser for 5fs pulse in the world.

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Compare to the similar experiment

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Generation fs pulse with other mediaCr:forsterite, Cr:YAG, Yb:YAG….

Ti:SapphireTi:Sapphire Cr:ForsteriteCr:Forsterite Cr:YAGCr:YAG

1500 nm1500 nm800 nm800 nm 1300 nm1300 nmEmission spectra of typical tunable laser crystals

Nd:glass and Yb:glass, produce 60 fs Opt Lett.22, 307,1997Yb:glass produce 60 fs Optics Lett. 23, 126, 1998Cr:LiSAF produce 45 fs Optics Lett. 22, 621, 1997

Some progresses:

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照片

1030 1064

Lasing regionLarger interval

1100 1400

M1~M3：100mm ROC ReflectorM4&M5: Chirped mirrors.Cr:forsterite：Gain medium in 10mm length

Experiment of fs Cr:forsterite laser

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Specifications

-75 -50 -25 0 25 50 750

2

4

6

8

Pulse duration: 29fsOutput power: 105mW Central wavelength: 1285nmBandwidth: 60nmRepetition rate: 82.6MHz Stability:

23

Advantage and disadvantage of Ti:S laserShort pulse: ≈ 5 fs, High gain

Low energy and average power: ~10nJ, 500mWIndirectly pump: Large size and low efficiency

Today, diode pump femtosecond laser show a new direction in future.Yb:YAG thin-disk laser: 60 W average output power

Picosecond regime: 6-24 ps, 34 MHz, 1.8 µJ, < 280 kWFemtosecond regime: 720 fs, 34 MHz, 1.7 µJ, 2.1 MW

Yb:KYW thin disk laser: 22 W average output power240 fs, 25 MHz, 0.9 µJ, 3.3 MW, focusable intensity:2 x 1014 W/cm2

Yb:YAG thin disk laser + pulse compression: 24 fs, 0.56 µJ, 57 MHz, Opt. Lett. 28, 1951, 2003

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Next generations of femtosecond lasersDiode directly pumped fs solid-state laserHigh average power: up to 100W High efficiency: up to 40％Compact sizeLonger pulse: ~100fs

Femtosecond fiber laserAverage power: up to 200mW Ultra-compact size.Long pulse: 100fs~200fs

Er: fiber laser: 1570nm/200fs/150mWSHG: 785nm/100fs/20mWAn ideal seeding for Ti:S laser amplifier with 100fs pulse

Yb:fiber: 1030nm/200fs/200mWDirectly amplification by diode laser pump

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Outline

Femtosecond generationSynchronization Carrier-envelope phase controlAmplification Route toward attosecond worldSummary

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Motivation of synchronizing fs laser

λ2

λ1

Detector

Probe laser

Pump laser

In many applications, femtosecond laser with single wavelength is not enough. For the researches on pump-probe spectroscopy, generation of difference frequency, fast ignition laser fusion etc, synchronization between different lasers is necessary.

A.Leitensdorfer et al; Opt Lett, Vol. 20, 916(1995)

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Passively synchronize two fs laser

Opt Opt LettLett, Vol.26,1806 (2001), , Vol.26,1806 (2001), ApplAppl Phys B, Vol74.S171, (2002)Phys B, Vol74.S171, (2002)

S-P Millennia Xs

S-P T-40Z-106C

P1

RG

P3

M5

HR

PZT P2P4

M1

PD

M4

M6

M3M2

T1

Cr:F

M7 SESAM

T2

Ti:S

PD

To AC and CC

PZT Driver

F2F1

Ti:sapphire laser600mW/18fs/820nm

Cr:forsterite laser200mW/42fs/1300nm

For the first we realized the synchronized femtosecond laser with different gain media, the timing jitter is less than 1fs

150

200

250

300

3500 1 2 3 4 5 6 7

f rep(7

5,76

1***

Hz)

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Average power: >1WPulse duration: 30~70fsTunable range: 740~850nmTiming jitter: 10µm

Stable synchronized fs Ti:sapphire laser

Opt Lett, Vol.26,1806 (2001), Opt Lett,Vol.30, 2121 (2005),

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The layout of the configuration for measurement of the cross correlation traces. B.S: Metal beam splitter. The signals of cross-correlation and two autocorrelations were dispersed with the grating for easy observation.

PZT Driver

PZT

PMT

BBO

B.S

Grating

Oscilloscope

1250

nm/6

5fs

Cr:

fors

terit

ela

ser

820nm/54fsTi:sapphire laser

Measurement of timing jitter

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The SFG of Ti:sapphire and Cr:forsterite lasers. FWHM corresponding to the SFG cross correlation trace is 74± 2fs.

Timing jitter of synchronized Ti:S and Cr:F laser

1.0

0.8

0.6

0.4

0.2

0.0

Nor

mal

ized

Inte

nsity

-150 -100 -50 0 50 100 150Time Delay (fs)

FWHM:74± 2fs

50

40

30

20

10

0Inte

nsity

of S

FG(a

.u)

543210Time(s)

V=41.424( average)∆V = 0.494438 (standard deviation )

∆Κ ⇔ ∆ V/V

Intensity fluctuation at half maximum of cross correlated trace between two lasers can be taken as linearly proportional to the timing jitter. We deduced the timing jitter is 0.7fs at 1kHz bandwidth over 5s.

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Cross-correlation trace (left) and the intensity fluctuation at half amplitude (right)

Timing jitter of synchronized Ti:Sa lasers

The measured cross-correlation trace shows a typical FWHM of about 60 fs, We deduced the timing jitter is 0.4fs at 1kHz bandwidth over 5s.

Jinrong.Tian, Zhiyi Wei et al, OL, Aug 15. (2005).

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Sum frequencylaser

1064nm ML Nd:YVO4Laser， 1W/7ps

ML Ti:S Laser, 700mW/50fs

816MHzPLL

68MHzPLL

Cavity lengthControl

BBO

lengthadjustment

Spectrometer

Oscilloscope

Active Synchronized two different lasers

ps laser:1064nm/488ps/10W, fs laser: 800nm/50fs/600mW

Poster

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Sum frequency generation

1064nm 810nm 532nm 460nm 405nm

spots distribution through a triple

prism

The technique open a new way to generate stable femtosecond laser pulse at new wavelength.

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Outline

Femtosecond generationSynchronizationCarrier-envelope phase controlAmplification Route toward attosecond worldSummary

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F

∆φ

f

δFF

fn=nF+δ f2n=2nF+δ

Carrier-envelope phase of fs laserControl the carrier envelope phase offset (CEO) is a very important topics in ultrafast science and frequency metrology.

E(ω,t) =E0(t)exp(iω t+φ)CEO lead to the comb shift

∆φ =2πδ /FRepetition rate

f=c /2nlLongitudinal mode frequency

fn=δ + nFf2n –2fn = δ + 2nF - 2( δ + nF )=-δ

⎯D.J.Jones et al., Science 288, 635(2000)

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Home-made fsTi:sapphire laser

λ/2λ/2

λ/2

KTP GratingAPD

APD

Fiber

Self-reference technique

f =nF+ δ

Stabilizing laser cavity length for locking frepModulating pump power for locking δ

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Layout of experiment for CEP controlantenna

TV-Rb clcok10MHz

PLLfor frep

PLLfor C

EP

PCF

Grating

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38200 400 600 800 1000 1200

0.01

0.1

1

Inte

nsity

/ a.

u.

Wavelength / nm

101

102

103

400 500 600 700 800 900 1000 1100

Inte

nsity

(arb

.uni

ts)

Wavelength(nm)

White continuum with photonic crystal fiber

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Locking of repetition rate

Without Locking

Locking

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Before locking:～10-7 After locking:～10-12

Comparison

The uncertain of repetition rate: ∆F＝10MHz×10-12～10mHzWe need more high precision clock

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Increasing of beat frequency signal

0.0 20.0 40.0 60.0 80.0 100.0 120.0

-80

-70

-60

-50

-40

-30

-20

-10

S/N

dB

Frequency(MHz)

About 50 dB

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0 50 100 150 200 250 300 3500

102030405060708090

Locking

RF

freq

uenc

y(M

Hz)

Time(s)

W ithout Lockingfceo

frep

0 50 100 150 200 250 300 350

6

8

10

12

14

16

18

20

RF

freq

uenc

y(M

Hz)

Time(s)

Without locking

Locking

Locking of CE phase with TV-Rb clock

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Performance of beat frequency with PCFUltrabroaden spectrum, cover from blue to infrared range.No special need for laser power and pulse duration.Very sensitive for beam point direction, any slight shift will lead to the CEP control unstable.The surface of fiber easily to be damaged, can not running for long time.Larger transmission loss lead to the lower output power.A complicate electronics is necessary to control the repetition rate and CEP frequency

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δf2=δ+nfrepf1=δ+mfrep

frep frepf

I (f)

fDFG= (m-n)frep

DFG: 627-1000nm⇒1680nm(ω)Free CE phase, f1 = nfrep

SHG: 1680nm ⇒840nm(2ω)Free CE phase, f2 = 2nfrep

DFG: Difference frequency generation:fDFG= f1 -f2= (δ+mfrep)-(δ+nfrep)= (m-n)frep

Optical frequency comb with DFG

DFG of the ultra-broaden band laser spectrum will generate a self-stabilized femtosecond frequency comb at wavelength around 1.5micrometer.

M. Zimmermann et al., MPQ; T. Fuji et al., TUW; S. M. Foreman et al., JILA&MIT

δδ =−−+−=− reprepDFG fnmfnmff )())[(

Beat signal

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F M1 M2X

M3OCW Ag

WM4

M5

Auto-Correlator

Dispersion compensation

M1~M5:Chirped Mirrors; W: wedges; OC: 10% Output couplerX: 2mm Ti:sapphire crystal; F: 50mm focus lens.

Experimental layout for dispersion adjust

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Experimental of DFG

Pump laser

CM

W

PP-MgO:LN

LFPD

CM: Chirped Mirrors, W:Wedges, LF: Long pass filter, PD: Photo diode for infrared, AOM: AO modulator

7fs Ti:s OscillatorAOM Ag Mirror

Ag Mirror

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Beat frequency spectrum

Beat frequency (fceo: 30dB)

0 40 80 120 160 200

-80

-70

-60

-50

-40

-30

-20

Pow

er sp

ectru

m(d

Bm

)Frequency(MHz)

1100 1200 1300 1400 1500 1600 17001E-3

0.01

0.1

1

Inte

nsity

(arb

.uni

t)

Wavelength(nm)

Spectrum of DF laser

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Control Cs clock with GPS receiver

GPS receiver

Cs clock

Function generator～

20GHz

Control F

Control fceo

10MHz

10MHz

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Electronics system for frequency locking

Fs laser

8GHz electrical

pulse

160MHz signal

8GHz Band filter

Low pass amplifier

To PZT

Low pass filter

comparator

GPS receiverCs clock

Function generator

8GHz Band filter

Low pass filter

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Stability of Cs clock

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Locking repetition rate with high accuracy

0 200 400 600 800

-40

-20

0

20

40

Freq

uenc

y(uH

z)

Time(s)

Locking the 50th harmonic of repetition rate 8GHz with the function generator, It leads to an accuracy of µHz

We design and made the PLL electronics to control cavity length by PZT

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Locking CEP by control the AOM

0 200 400 600 800 1000

19.6

19.8

20.0

20.2

20.4

CEO

Fre

quen

cy(M

Hz)

Time(s)

20000018

20000018.5

20000019

20000019.5

20000020

20000020.5

20000021

20000021.5

21:59:22.0

22:00:33.0

22:01:43.0

22:02:53.0

22:04:04.0

22:05:14.0

22:06:25.0

22:07:35.0

22:08:46.0

22:09:56.0

22:11:07.0

22:12:17.0

22:13:27.0

22:14:38.0

22:15:48.0

22:16:59.0

系列1

1800000018500000190000001950000020000000205000002100000021500000220000002250000023000000

00:00:00.0

00:00:25.1

00:00:50.3

00:01:15.4

00:01:40.9

00:02:06.2

00:02:31.5

00:02:56.8

00:03:22.1

00:03:47.4

00:04:12.6

00:04:37.9

00:05:03.0

00:05:28.1

系列1

Before locking:The fluctuation of fceowithin 5min is about 3MHz

After locking:The fluctuation of fceowithin 17min is only 2Hz

We use the Menlo Inc electronics to control the CEP frequency by AOM

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Fluctuations after optimized locking

0 100 200 300 400 500 600-30

0

30

60

90

120

150

180

B

A

Freq

uenc

y(m

Hz)

Time(s)A. The fluctuation of locked repetition rateB. The fluctuation of locking fceo

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Outline

Femtosecond generationSynchronization Carrier-envelope phase controlAmplification Route toward attosecond worldSummary

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55t

Chirped Pulse Amplification

D. Strickland and G. Mourou, Optics Commun. 56, 219 (1985)

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Development of laser powerDevelopment of laser power

gth νσν

∆=hP

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Extreme Light-I（1999）Pulse Energy：36mJDuration：25fsPeak Power：>1.4TW

Extreme Light-II （2001)Pulse Energy: 640mJDuration：31fsPeak Power: ~20TW

TW laser facilities at IOP

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High Efficiency in Final AmplifierRun above the saturation fluency

Solid State Amplifier Desires

Produce the shortest duration pulsesRun near the fluorescence limit

No DamageRun below the dielectric breakdown limit< 5x109 W/cm2

Jsat

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Maximum Intensity at Saturation

Conclusion: We must reduce pulse INTENSITYduring amplification

Maximum output intensity = Jsat / ∆tmin

Material Jsat(J/cm2)∆tmin

(fs)Imax

Nd:Silicate 6 60 1014

Yb:Silicate 32 20 1.6x1015

Ti:Sapphire 1 3 3.3x1014

(W/cm2)

However, damage threshold

60

Inverse delay line

t

t

Dispersive delay line

General Chirped Pulse Amplification

Peak Power Increase Proportional to∆tstretch > 1000

t

Short pulse oscillator

∆tstretch = Jsat/IdamageNd:Glass ~ 1 ns Ti:Al2O3 ~ 200 ps

t

Solid state amplifiers

Saturation is Reached Safely

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Classification of stretcherMartinez Stretcheraberration, can not compress pulse shorter than 50fsÖffner Stretcherfree aberration, most widely useMaterial StretcherUse high dispersion material, suit for 10fs⇒ ~10ps

2f

L1(f) L2(f)

Red

Blue

Graing1Graing2

L L

O

SF57

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Gain narrowing effectGain narrowing effect

⎥⎦⎤

⎢⎣⎡= ⎟⎠

⎞⎜⎝⎛ωωω χ ''exp)(

cLG

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Approaches to Gain Narrowing ControlMinimize systems losses

Multi-pass amplifiers with high gain per passSeed to the RED of the line center

Regen or multi-passPlay off saturation pulling against gain shifting

Mix amplifier materialsDifferent center frequency yields higher overall gain bandwidth

Regenerative pulse shapingCorrect for the gain narrowing on each pass trip

OPCPA (Optical Parametric CPA)Large gain bandwidth in parametric amplification

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Regenerative Pulse Shaping

Relatively low gain per pass means we only need a linear filter

Thin Film PolarizerHR

532 nm Pump

Injected PulseAmplified Pulse

10 pass preamplifier10 pass preamplifier

Polarizer

Pockels cell

Berek

Polarizer

Periscope

Z.Cheng ,F.Krausz, Ch.Spielmann, Opt. Commun 201, 145 (2002)

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Optical Parametric CPA(OPCPA)

OPASeedpulse

Outputpulse

Pump pulse

Stretching, shaping, timing

Compressor

Laser amplifier is replaced by OPA

A.Dubietis, G.Jonušauskas, A.Piskarskas, Opt. Commun, 88, 437 (1992)

from 100 fs to 10 ns

BBO, LBO, CLBO, RTP, KTA, KDP, DKDP,YCOB…

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OPCPA VS. CPA BASED ON A GAIN MEDIUM OPCPA CPA based on Ti:Sa crystal

Gain bandwidth >100THz ~ 30 THz

Single-pass gain ~ 106 < 10

B-integral Low < 1.0 High > 1.0

Thermal load Negligible (-> high repetition rate)

Non-thermal lensing effect

Huge (-> low repetition rate)

Thermal lensing effect

Storage of energy Instantaneous

(Strict synchronization ~ ps)

~ µs

( Relaxed synchronization ~ ns)

Pedestal Amplified superfluorescence Amplified spontaneous emission

Gain wavelength Variable Fixed

ADVANTAGES:Extremely broad gain bandwidthHigh gain in single pass Low thermooptics (high output beam

quality)High contrast ratio (reduced ASE)

DISADVANTAGES:No pump energy accumulation (high intensity

pump required)Losses introduced by idler wave Limited aperture of nonlinear crystalsPrecise pump/signal synch. required

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Shortest pulses from OPCPA by year[1] A. Dubietis et al, Opt. Commun. 88, 437 (1992)

[2] V.V. Yakovlev et al, Opt. Lett. 19, 2000 (1994)

[3] G. Cerullo et al, Appl. Phys. Lett. 71, 3616 (1997)

[4] A. Shirakawa et al, Opt. Lett. 23, 1292 (1998)

[5] A. Shirakawa et al, Appl. Phys. Lett. 74, 2268 (1999)

[6] A. Baltuška et al, Opt. Lett. 27, 306 (2002)

OPA crystal – BBO only

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PROGRESS IN OPCPA - BASED LASER SYSTEMS: TOWARDS HIGH OUTPUT POWERS

1992 1994 1996 1998 2000 2002 2004 20061E-4

1E-3

0.01

0.1

1

10

100

1000

10000

500GW [18]

10GW [11]

500GW [14]

1.07TW [15]

300GW [13]115GW [12]

350TW [16]200TW [17]

670GW [10]

4.5GW [9]10GW [6]

16,7TW [8]

1,3TW [3]

11PW [2]

180GW [7]

3,67TW [5]

50GW [4]

P

ower

, T

W

Years

0,9GW [1]

(Project)

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General design of multi-100TW laser

500 mJ/ 532nm/10HzSingle frequency laser

Oscillator20fs/5nJ/80MHz

OPCPA, 2mJ/10 Hz

Power amplification>30 J/single shot

Second stage~1J/800nm, 1Hz

Compressor20J/40fs/500TW

3J /532nm/1Hz

~100J/ 532nm pump laserSingle shot/about 20 min

Stretcher>600ps

Deformable mirror1.5DF/3×1020

1nJ

φ2106

φ160

φ40

500MW/cm2

φ14/7

φ60

Jp＝2J/cm2

Jp＝2J/cm2200mJ/cm2

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50J/527nm

pump laser

Am

plifier IIA

mplifier I

CW 532nmpump laser

fs oscillator500mW/20fs

20J/40fs～

500TW

Target Chamber II

Pre-pulseGenerator

600mJ/30fs

~20TW

Target Chamber I

Final amplifier~30J/800nm/20min

1mArea for power supply, 1X6 meters Control Platform

Door

Clear door

Room size:14X8 meters

Compressor I

50J/527nmPump laser

3J/532nm/1H

z

500mJ/10Hz532nm SF Laser

Compressor II

Arrangement for multi-100TW laser

Offern Stretcher

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Doubled trip stretcher

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Design and experiment of OPCPANd:YAG laser5ns/0.1J/532nm

DG535

Ti:S laser20fs/5nJ/800nm

E-O Gate

Stretcher: 0.6ns

100mJ 0.4J

Telescopy×

0.01

Telescopy×

0.3

Telescopy×0.18 Telescope×3.8

DM1 DM2 DM3 DM4

Delay Dealy

LBOOPAI

LBOOPAII

?800nm

compressorAfter OPAI

~60µJ

Problems: 1.Stable single frequency operation2.High energy necessary because of low efficiency

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Ti:S laser,5nJ 20fs/800nm/80MHz

Mode-Locking Nd:YVO4 laser,

500ps/1064nm/80MHz

TV-Rb clock10MHz

PLL Circuit for synchronized ps

and fs laser

Circuit for control cavity length

Regenerative amplifier pump

with DL100nJ

stretcher~ 500ps

Multi pass amp

2mJ1kHz

100mJ10Hz SHG

PC Dazzler

50mJ532nm

2mJ/10Hz800nm

A new design with high efficiency under construction

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LD pumped actively mode-locking Nd:YAG laser

M1

1746mm

Nd:YAG AOMOC

The locked phase loop

circuit

pin

PZT

82MHz referred frequency

Diagram of the all solid state active-mode locking Nd:YAG laser. The frequency is 82MHz

-1000 -500 0 500 1000

0.0

0.2

0.4

0.6

0.8

1.0

-1000 -500 0 500 1000

0.0

0.2

0.4

0.6

0.8

1.0

stre

ngth

coe

ffici

ent

d l i ( )

stre

ngth

coe

ffici

ent

d l i ( )

The autocorrelation trace of mode locked pulse. The full width is about 488 psec.

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Regenerative amplifier

Pump: 30mJ/532nm Output:~2mJ/800nm

PH3FI2

λ/2

MR1

MR2.HPH4

MR3

MR6

MR7

MP3

MR4H

MP2MP1 F3

TFP

From Stretcher

To oscilloscope for monitor the amplified train trace From 1kHz pump laser

F2F1

MR8

λ/4PIN MR5 To Main Amp

Glan Prism

PC1

Ti:S

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Acoustic-Optic Programmable Dispersive Filter for spectral amplitude and phase control

Slow Axis (mode 2)

Fast Axis(mode 1)

Acousticwave

Spectrum Shaping Control with AOPDF

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Spectra with shaping technique

Seeding pulse

Amplified pulse without AOPDF work

Amplified pulse with AOPDF work

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Multi-pass amplifier

Glan prism

PC 3 PC 4

λ/2

From Reg.

1Hz Nd:YAG2.6J@532nm

Glan prism

With 2.6J pump laser energy, amplified laser of 700mJ was obtained, corresponding to the efficiency of 27%

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Layout of 100J pump laser system

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Pump:527nm Nd:glass laser Energy:100J

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Expected result: 20J/40fs, >500TW

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85

～0.2米

～2.6米

MP1 晶体φ85×20mm

IR5

IR4

IR3

IR2

MP2

MP3MP4

MP5MP6

MP7

MP9

MP10

M2

M3

M4

M5

M6M7

M8

M9

M10

M11

M12

～2.0米～2.16米

～2.16米

～0.5米

～0.6米

～0.7米

～0.39米

0.11

～0.27米

PC

Design of final amplifier

Pumped the final amplifier with 80J laser at 527nm, laser energy only 5J was obtained at initial experiment.

The lower efficiency of amplification infer to the possible ASE

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Eliminate ASE and PL with index match material

Using thermoplastic (Cargille Laboratories, Inc.) material can well eliminate the effect.Amplified energy of 20J was obtained finally

1 : 2

21 2

21 2

1.76 1

( ) 7.6% 1/ 13( )

Ti sapphire airN N N N

N NR G RN N

= = = =

−= = = =

+

10 1

10 2

10 3

10 4

10 5

876543Beam Diameter /cm

Tran

sver

se G

ain

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Space size of the chamber：900×700mm,Incident angle: 24 degree，diffractive angle: 51degree

Vacuum pumps

Layout of vacuum compressor

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The record works on TW laser

The highest peak power—850WJAERI, Japan, K.Yamakawa et al, The highest power density— 0.8X1022W/cm2Michigan University, USA, S.Bahk et al, CLEO2004The highest peak power from OPCPA—500TWInstitute of Applied Physics, Russian The highest contrast ratio— 10-11 French, USA (Michigan PW) The shortest pulse duration— 1TW/10fs,10TW/12fsAIST Japan, H.Takada et al

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Improved beam quality for higher focusable intensitycorrect wave-front distortion, adaptive optics system.Spectrum shaping for shorter pulse durationSLM (spatial liquid crystal modulator)Acoustic-optics modulatorPhase controlling for stronger nonlinear interactionCarrier Envelope Phase control.Eliminate the ASE for a higher contrast ratio.Spatial filter, Pockels Cells.OPCPA-Optical Parametric Chirped Pulse AmplificationDCPA，Absorber

Optimize CPA laser with new techniques

Contrast ratio: 10-10 ~10-11CLEO: 2005

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OutlineFemtosecond generationSynchronization Carrier-envelope phase controlAmplification Route toward attosecond worldSummary

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Compression laser pulse to 5fsCompression laser pulse to 5fs

Ne gas

25 fs1.8 mJ 5 - 7 fs0.9 mJ

1kHz amplifier Femtolaser Inc

Ag mirrorChirped mirror

Wedge pair

Ag mirror Ag mirror

Chirped mirror

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Pulse duration and spectrum after optimized compression

-30 -20 -10 0 10 20 300

2

4

6

8

Inte

nsity

(arb

.uni

ts)

Time(fs)

5.1fs

600 700 800 900 10000

100

200

300

400

Inte

nsity

(arb

.uni

ts)

Wavelength(nm)

Pulse duration of shorter than 4fs should be possible by further optimizing the dispersion balance

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Generation of attosecond HHG X ray laser

Drescher et al. Science 291 1923 (2001)

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97100100200300100200100Multi-Waves Power (mW)

400300200400200Multi-Waves Power (mW)

2001004003002001000500Single Max Power (mW)

80802050501020Pulse Duration (fs)

32337043051664586012902580Wavelength (nm)

2ω +6ω3ω

+5ω

3ω +4ω2ω

+5ω

3ω +3ω

3ω + 2ω

2ω + 2ω

Ti:Al2O3

Cr:Mg2SiO4

Waves Relation

8ω 7ω 6ω 5ω 4ω 3ω 2ω ω Harmonic Wave Order

Generation of fs sub-harmonic waves

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Coherent synthesization for sub-fs pulse

Assump the duration is 5fs for each pulse, the coherent synthesization will lead to sub-1fs laser pulse.

1200nm2ω

800nm3ω

600nm4ω

480nm5ω

400nm6ω

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Research activities in our groupResearch activities in our groupAmplify femtosecond laser to multi-100TWOptical frequency comb and frequency metrologyGeneration of few cycle laser pulseGeneration of attosecond laser pulse5.1fs/400µJ/1kHzFemtosecond Cr:forsterite laser 29fs/200mW, all chirp mirrors, 1030nm PumpSynchronization of femtosecond laser pulsesub-fs timing jitter, long-term stability, commercial designFs and ps OPO, OPAfs OPO with PPLN, 30mW/1050~1250 nm, OPA: 200~700nm/ps/>10mJDiode pumped fs and ps solid-state laserQuasi-three level Nd doped lasers (CW, SHG & ML):GdVO4(912/456nm), LuVO4(916/458nm), GSAG(942nm)

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SummaryNovel technologies for femtosecond laser

generation, synchronization, phase control and amplification are reviewed.

We developed an oscillator with CM technique, pulse of as short as 7fs was directly generated. As our best knowledge, this is the simplest laser configuration for sub-10fs laser pulse.

Passive and active synchronization with low timing jitter were developed, a feasible new way to generate femtosecond laser pulse by sum frequency was proposed

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Difference frequency the ultrabroaden spectrum with a PP-MgO:LN crystal, we obtained a beat frequency with S/N ratio of about 30dB. Locking the signal and repetition rate to a Cs clock with GPS receiver, we demonstrated a frequency comb with uncertainty of 2×10-15

Base on our previous works on TW Ti:sapphire lasers, a new facility (Extreme III) was designed. With the home-designed pump laser, the system will be capable of peak power of multi-100TW.

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Acknowledgement for CollaboratorsJie Zhang, Professor of IOPStaffs: Prof Yuxin Nie, Naicheng Shen, Dr Hao Teng, Mr Dehua Li, Prof Zhiguo Zhang Post-doctor, Zhaohua Wang, Qiang DuGraduated Ph D Students：Hainian Han (TsingHua Uni), Weijun Ling(Xian IOPM)Jinrong Tian(BTU, Beijing), Yulei Jia (Shang Dong Uni)Ph Students:Peng Wang, Yanying Zhao, Jiangfeng Zhu, Huan Zhao, Wei Zhang, Binbin Zhou, Xin Zhong and Changwen Xu

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Thank You for your attention!

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