飞秒激光产生与控制

国家自然科学基金委员会 

数理学部实验物理讲习班 

Management of femtosecond laser pulse 

--Generation, synchronization, phase control and 

amplification 

Zhiyi Wei 

Institute of Physics 

Chinese Academy of Sciences 

Beijing 100080, China



Outline 

Femtosecond generation 

Synchronization 

Carrier-envelope phase control 

Amplification 

Route toward attosecond world 

Summary 

2



Outline 




Amplification 


Summary 

3



A history of pursue time limit 

Toward Monocycles pulse (



Mechanism: 

Type: 

Starting: 

Activity: 

Parameters 

How to get very short pulse 

--- Advanced mode locking techniques 

Kerr Lens Mode 

Locking 

Passive 

Non self starting 

Push or tap 

mirror 

< 10 fs, >100 nm 

Active mode 

locking by AOM 

Active 

Modulator 

Modulator 

always on 

< 100 fs 

Saturable bragg 

reflectors (SBR) 

Passive 

Self starting 

SBR as cavity 

mirror 

< 20 fs, > 40 nm 

Large bandwidth: with Fourier Transform limit: Δν Δτ < 0.314 

laser medium should has a wider gain band. Dye, Ti:sapphire. 

Dispersion compensation: consider high order dispersion. 

the large bandwidth, the difficult for compensation 

5



Kerr Lens Mode-locking laser 

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

6



Dispersion control in Ti:sapphire laser 

8.5fs 

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

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. 

7



What is chirped mirror 

the perfect source for negative GDD 

8



Prism controlled Ti:sapphire laser 

600mm 

Size:600mm×200mm×150mm 

200mm 

Stability 1W 

Pulse duration 15~30fs 

Peak Power ~1MW 

Tunable range 760nm~850nm 

Repetition rate 50~100MHz 

9



Intensity 

8 

7 

6 

5 

4 

3 

2 

1 

Pulse duration and stability 

Ultralasers 

0 

-40 -20 0 20 40 

Time delay (fs) 



Chirped mirror Ti:sapphire laser 

M3 

5W 532nm Millennia 

f=10 cm M1 M2 

Ti:sa 

OC T=10% 

M1-M3: Chirped mirrors, F≈ 160 MHz 

11



Dispersion of Ti:S crystal and chirped mirror 

Dispersion of Ti:sapphire (1mm) 

100 

75 

50 

25 

0 

-25 

-50 

GDD, fs 2 

TOD, fs 3 

-75 

0.6 0.7 0.8 0.9 1.0 

wavelength /μm 

FOD, fs 4 

Dispersion /fs 2 

-100 

-150 

-200 

650 700 750 800 850 900 950 10001050 

Ti:sapphire crystal Chirped mirror 

100 

50 

0 

-50 

wavelength /nm 

12



Refractive index and dispersion of air 

Refractive index of air 

1.000279 

1.000278 

1.000277 

1.000276 

1.000275 

0.5 0.6 0.7 0.8 0.9 1.0 


Dispersion of air 

30 

25 

20 

15 

10 

5 

Dispersion of 1m air 

0 

0.6 0.7 0.8 0.9 1.0 


The dispersion of air is 21.3 fs2 per 1meter at wavelength of 

800nm, it enables us to accurately adjust dispersion by air 

GDD, fs 2 

TOD, fs 3 

FOD, fs 4 

13



Spot size /μm 

M3 

600 

500 

400 

300 

200 

100 

Spectra with SPM effect 

F M1 X M2 

0 

0 100 200 300 400 500 600 700 800 

Z /mm 

f = Infty 

f = 30cm 

f = 20cm 

OC 

Intensity 

1.0 

0.8 

0.6 

0.4 

0.2 

532 nm 

x=0.3 mm 

x=0.2 

x=0.1 

1064 nm 

0.0 

500 600 700 800 900 1000 1100 


We calculate the waist size inside 

the Ti:Sa crystal is 10.9 μm, Moving 

M2 will lead to the change of SPM 

14



Optimized ultrabroaden spectrum 

Spectral intensity 

1.0 

0.8 

0.6 

0.4 

0.2 

532 nm 

0.0 

500 600 700 800 900 1000 1100 


1064 nm 

Directly output from the oscillator, covered from 550~1050nm 

We generated the quasi-octave spanning spectrum with the 

simplest laser configuration 

15



Measurement of laser pulse 

Sub-10fs oscillator 

autocorrelator 

Wedges 

Chirped 

mirror 

Ag mirror 

Ag mirror 

Chirped 

mirror 

Layout Interferometer autocorrelator 

16



Intensity (arb.units) 

8 

6 

4 

2 

Pulse duration and spectrum 

7fs 

0 

-30 -20 -10 0 10 20 30 

Time(fs) 

Intensity(a.u) 

600 700 800 900 1000 

One of the shortest pulse generated with the simplest laser 

configuration in the world. 7fs/300mW/160MHz 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 

Wavelength(nm) 

17



Compare to the similar 

experiment 

18



Generation fs pulse with other media 

Cr:forsterite, Cr:YAG, Yb:YAG…. 

Ti:Sapphire Cr:Forsterite Cr:YAG 

800 nm 1300 nm 

1500 nm 

Emission spectra of typical tunable laser crystals 

Some progresses: 

Nd:glass and Yb:glass, produce 60 fs Opt Lett.22, 307,1997 

Yb:glass produce 60 fs Optics Lett. 23, 126, 1998 

Cr:LiSAF produce 45 fs Optics Lett. 22, 621, 1997 

19



Experiment of fs Cr:forsterite laser 

M1~M3:100mm ROC Reflector 

M4&M5: Chirped mirrors. 

Cr:forsterite:Gain medium in 10mm length 

Larger interval 

1030 1064 

Lasing region 

1100 1400 

照片 

20



Specifications 

Pulse duration: 29fs 

Output power: 105mW 

Central wavelength: 1285nm 

Bandwidth: 60nm 

Repetition rate: 82.6MHz 

Stability:



Advantage and disadvantage of Ti:S laser 

Short pulse: ≈ 5 fs, 

High gain 

Low energy and average power: ~10nJ, 500mW 

Indirectly 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 kW 

Femtosecond regime: 720 fs, 34 MHz, 1.7 µJ, 2.1 MW 

Yb:KYW thin disk laser: 22 W average output power 

240 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 

22



Next generations of femtosecond lasers 

Diode directly pumped fs solid-state laser 

High average power: up to 100W 

High efficiency: up to 40% 

Compact size 

Longer pulse: ~100fs 

Femtosecond fiber laser 

Average power: up to 200mW 

Ultra-compact size. 

Long pulse: 100fs~200fs 

Er: fiber laser: 1570nm/200fs/150mW 

SHG: 785nm/100fs/20mW 

An ideal seeding for Ti:S laser amplifier with 100fs pulse 

Yb:fiber: 1030nm/200fs/200mW 

Directly amplification by diode laser pump 

23



Outline 




Amplification 


Summary 

24



Motivation of synchronizing fs laser 

In many applications, femtosecond laser with single 

wavelength is not enough. For the researches on pumpprobe 

spectroscopy, generation of difference frequency, 

fast ignition laser fusion etc, synchronization between 

different lasers is necessary. 

λ2 

Probe laser 

λ1 

Detector 

Pump laser 

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

25



PZT 

Passively synchronize two fs laser 

HR 

P2 

PZT Driver 

F2 

S-P T-40Z-106C 

P1 

Cr:F 

M5 

M7 SESAM 

M4 

M2 

M6 

Ti:S 

M1 

S-P Millennia Xs 

P3 

M3F1 

Opt Lett, Lett, 

Vol.26,1806 (2001), 

Appl Phys B, Vol74.S171, (2002) 

P4 

T1 

T2 

RG 

PD 

To AC 

and CC 

For the first we realized the 

synchronized femtosecond laser 

with different gain media, the 

timing jitter is less than 1fs 

PD 

f rep (75,761***Hz) 

300 

250 

200 

150 

Ti:sapphire laser 

600mW/18fs/820nm 

Cr:forsterite laser 

200mW/42fs/1300nm 

0 1 2 3 4 5 6 7 

350 

26



Stable synchronized fs Ti:sapphire laser 

Average power: >1W 

Pulse duration: 30~70fs 

Tunable range: 740~850nm 

Timing jitter: 10μm 

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

27



1250nm/65fs 

Cr:forsterite laser 

820nm/54fs 

B.S 


Measurement of timing jitter 

PZT 

Driver 

PZT 

BBO 

Oscilloscope 

Grating 

PMT 

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. 

28



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

Normalized Intensity 

1.0 

0.8 

0.6 

0.4 

0.2 

FWHM: 

74± 2fs 

0.0 

-150 -100 -50 0 50 100 150 

0 

0 1 2 3 4 5 

Time Delay (fs) 

Time(s) 

The SFG of Ti:sapphire and Cr:forsterite lasers. FWHM corresponding to 

the SFG cross correlation trace is 74± 2fs. 

Intensity of SFG(a.u) 

50 

40 

30 

20 

10 

V=41.424( average) 

ΔV = 0.494438 (standard deviation ) 

ΔΚ ⇔ Δ 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. 

29



Timing jitter of synchronized Ti:Sa lasers 

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

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). 

30



Active Synchronized two different lasers 

1064nm ML Nd:YVO4 

Laser, 1W/7ps 

ML Ti:S Laser, 

700mW/50fs 

Cavity length 

Control 

816MHz 

PLL 

68MHz 

PLL 

Spectrometer 

Poster 

BBO 

length 

adjustment 

Sum frequency 

laser 

Oscilloscope 

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

31



Sum frequency generation 

spots distribution 

through a triple 

prism 

The 1064nm technique 810nmopen 532nm a new way 460nm to generate stable 405nm 

femtosecond laser pulse at new wavelength. 

32



Outline 




Amplification 


Summary 

33



Carrier-envelope phase of fs laser 

Control 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 

Δφ =2πδ /F 

F 

Repetition rate 

f=c /2nl 

Longitudinal mode frequency 

fn=δ + nF 

f 2n –2f n = δ + 2nF - 2( δ + nF )=-δ 

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

F 

F 

δ 

Δφ 

f n =nF+δ f 2n =2nF+δ 

f 

34



λ/2 

f =nF + δ 

Self-reference technique 

Fiber 

λ/2 

Home-made fs 


λ/2 

APD 

KTP APD 

Grating 

Stabilizing laser cavity length for locking frep Modulating pump power for locking δ 

35



Layout of experiment for CEP control 

PLL 

for CEP 

Grating 

PLL 

for frep TV-Rb clcok 

10MHz 

PCF 

antenna 

36



Intensity / a.u. 

1 

0.1 

0.01 

White continuum with 

photonic crystal fiber 

200 400 600 800 1000 1200 

Wavelength / nm 

Intensity(arb.units) 

10 3 

10 2 

10 1 

400 500 600 700 800 900 1000 1100 


37



Locking of repetition rate 

Without Locking 

Locking 

38



Comparison 

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

The uncertain of repetition rate: ΔF=10MHz×10-12 ~10mHz 

We need more high precision clock 

39



Increasing of beat frequency signal 

S/N dB 

-10 

-20 

-30 

-40 

-50 

-60 

-70 

-80 

0.0 20.0 40.0 60.0 80.0 100.0 120.0 

Frequency(MHz) 

About 50 dB 

40



Locking of CE phase with TV-Rb clock 

RF frequency(MHz) 

90 

80 

70 

60 

50 

40 

30 

20 

10 

f rep 

Without Locking 

f ceo 

RF frequency(MHz) 

20 

18 

16 

14 

12 

10 

8 

6 

Without locking 

Locking 

0 50 100 150 200 250 300 350 

Time(s) 

Locking 

0 

0 50 100 150 200 250 300 350 

Time(s) 

41



Performance of beat frequency with PCF 

Ultrabroaden 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 

42



DFG: Difference frequency generation: 

fDFG = f1 -f2 = (δ+mfrep )-(δ+nfrep )= (m-n)frep f − f DFG = [( m − n) 

f rep + δ ) − ( m − n) 

f rep = δ 

I (f) 

Optical frequency comb with DFG 

f 2 =δ+nf rep 

δ 

f 1 =δ+mf rep 

fDFG = (m-n)frep frep frep Beat signal 

DFG of the ultra-broaden band 

laser spectrum will generate a 

self-stabilized femtosecond 

frequency comb at wavelength 

around 1.5micrometer. 

f 

DFG: 627-1000nm⇒1680nm(ω) 

Free CE phase, f1 = nfrep SHG: 1680nm ⇒840nm(2ω) 

Free CE phase, f2 = 2nfrep M. Zimmermann et al., MPQ; T. Fuji et al., TUW; S. M. Foreman et al., JILA&MIT 

43



Experimental layout for dispersion adjust 

M3 

W 

Auto-Correlator 

F M1 X M2 

M4 

M5 

W 

OC 

Ag 

Dispersion 

compensation 

M1~M5:Chirped Mirrors; W: wedges; OC: 10% Output coupler 

X: 2mm Ti:sapphire crystal; F: 50mm focus lens. 

44



Pump laser 

Experimental of DFG 

AOM 

7fs Ti:s Oscillator 

CM 

PD 

W 

PP-MgO:LN 

CM: Chirped Mirrors, W:Wedges, LF: Long pass filter, 

PD: Photo diode for infrared, AOM: AO modulator 

LF 

Ag Mirror 

Ag Mirror 

45



Intensity(arb.unit) 

1 

0.1 

0.01 

1E-3 

Beat frequency spectrum 

1100 1200 1300 1400 1500 1600 1700 


Spectrum of DF laser 

Power spectrum(dBm) 

-20 

-30 

-40 

-50 

-60 

-70 

-80 

0 40 80 120 160 200 

Frequency(MHz) 

Beat frequency (fceo: 30dB) 

46



Control Cs clock with 

GPS receiver 

GPS receiver 

Cs clock 

10MHz 

Function 

generator~ 

20GHz 

10MHz 

Control F 

Control fceo 

47



Electronics system for frequency locking 

Cs clock 

Function 

generator 

Fs laser 

To PZT 

8GHz 

electrical 

pulse 

160MHz 

signal 

8GHz 

Band filter 

8GHz 

Band filter 

GPS receiver 

Low pass 

amplifier 

Low pass 

filter 

Low pass 

filter 

comparator 

48



Stability of Cs clock 

49



Locking repetition rate with high accuracy 

Locking the 50th 

harmonic of repetition 

rate 8GHz with the 

function generator, It 

leads to an accuracy 

of μHz 

Frequency(uHz) 

40 

20 

0 

-20 

-40 

0 200 400 600 800 

Time(s) 

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

50



CEO Frequency(MHz) 

20.4 

20.2 

20.0 

19.8 

19.6 

Locking CEP by control the AOM 

Before locking: 

The fluctuation of fceo 

within 5min is about 3MHz 

0 200 400 600 800 1000 

Time(s) 

After locking: 

The fluctuation of fceo 

within 17min is only 2Hz 

23000000 

22500000 

22000000 

21500000 

21000000 

20500000 

20000000 

19500000 

19000000 

18500000 

18000000 

00:00:00.0 

00:00:25.1 

20000021.5 

20000021 

20000020.5 

20000020 

20000019.5 

20000019 

20000018.5 

20000018 

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 

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 

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

系列1 

51 

系列1



Fluctuations after optimized locking 

Frequency(mHz) 

180 

150 

120 

90 

60 

30 

0 

B 

-30 

0 100 200 300 400 500 600 

A 

Time(s) 

A. The fluctuation of locked repetition rate 

B. The fluctuation of locking fceo 52



Outline 




Amplification 


Summary 

53



Chirped Pulse Amplification 

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

54 

t



Development of laser power 

P 

th 

hν 

= Δν 

g 

σ 

55



TW laser facilities at IOP 

Extreme Light-I(1999) 

Pulse Energy:36mJ 

Duration:25fs 

Peak Power:>1.4TW 

Extreme Light-II (2001) 

Pulse Energy: 640mJ 

Duration:31fs 

Peak Power: ~20TW 

56



Solid State Amplifier Desires 

High Efficiency in Final Amplifier 

Run above the saturation fluency 

J sat 

Produce the shortest duration pulses 

Run near the fluorescence limit 

No Damage 

Run below the dielectric breakdown limit< 5x10 9 W/cm 2 

57



Maximum Intensity at Saturation 

Material 

Jsat 

(J/cm2 ) 

Δtmin 

(fs) 

Maximum output intensity = J sat / Δt min 

Imax 

(W/cm2 ) 

Nd:Silicate 6 60 10 14 

Yb:Silicate 32 20 1.6x10 15 

Ti:Sapphire 1 3 3.3x10 14 

However, damage threshold



General Chirped Pulse Amplification 

Short pulse 

oscillator 

t 

Dispersive delay line 

Solid state amplifiers 

Saturation is Reached Safely 

Δt stretch = J sat /I damage 

Nd:Glass ~ 1 ns 

Ti:Al2O3 ~ 200 ps 

Peak Power Increase Proportional to 

Δtstretch > 1000 

t 

t 

Inverse delay line 

t 59



Martinez Stretcher 

Classification of stretcher 

aberration, can not 

compress pulse shorter 

than 50fs 

Öffner Stretcher 

free aberration, most widely 

use 

Material Stretcher 

Use high dispersion material, 

suit for 10fs⇒ ~10ps 

Graing1 

Red 

L1(f) L2(f) 

Blue 

L 2f 

L 

SF57 

Graing2 

O 

60



⎡ω 

ω ⎢ χ 

⎣ 

' ' L 

G( 

) exp 

c 

= ⎜ 

⎛ 

⎟ 

⎞ ω ⎝ ⎠ 

Gain narrowing effect 

⎤ 

⎥ 

⎦



Approaches to Gain Narrowing Control 

Minimize systems losses 

Multi-pass amplifiers with high gain per pass 

Seed to the RED of the line center 

Regen or multi-pass 

Play off saturation pulling against gain shifting 

Mix amplifier materials 

Different center frequency yields higher overall gain 

bandwidth 

Regenerative pulse shaping 

Correct for the gain narrowing on each pass trip 

OPCPA (Optical Parametric CPA) 

Large gain bandwidth in parametric amplification 

62



HR 

Spectral Fliter 

c 

T( ω)= 

G( ω ) 

Regenerative Pulse Shaping 

Thin Film Polarizer 

Amplified Pulse 



Polarizer 

Pockels cell 

Periscope 

10 pass preamplifier 

Polarizer 

Berek 

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



Seed 

pulse 

Optical Parametric CPA(OPCPA) 

Stretching, 

shaping, 

timing 

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

Pump 

pulse 

OPA 

Compressor 

Laser amplifier is replaced by OPA 

Output 

pulse 

from 100 fs to 10 ns 

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

65



OPCPA VS. CPA BASED ON A GAIN MEDIUM 

OPCPA CPA based on Ti:Sa crystal 

Gain bandwidth >100THz ~ 30 THz 

Single-pass gain ~ 10 6 < 10 

B-integral Low < 1.0 High > 1.0 

Thermal load Negligible (-> high repetition rate) 

Non-thermal lensing effect 

Storage of energy Instantaneous 

(Strict synchronization ~ ps) 

Huge (-> low repetition rate) 

Thermal lensing effect 

~ µs 

( Relaxed synchronization ~ ns) 

Pedestal Amplified superfluorescence Amplified spontaneous emission 

Gain wavelength Variable Fixed 

ADVANTAGES: 

Extremely broad gain bandwidth 

High 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 crystals 

Precise pump/signal synch. required



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 

67



General design of multi-100TW laser 

Oscillator 

20fs/5nJ/80MHz 

Stretcher 

>600ps 

Compressor 

20J/40fs/500TW 

Deformable mirror 

1.5DF/3×10 20 

1nJ 

φ2 

φ160 

200mJ/cm 2 

500 mJ/ 532nm/10Hz 

Single frequency laser 

500MW/cm 2 

OPCPA, 

2mJ/10 Hz 

φ60 

10 6 

φ14/7 

Power amplification 

>30 J/single shot 

J p =2J/cm 2 

~100J/ 532nm pump laser 

Single shot/about 20 min 

3J /532nm/1Hz 

J p =2J/cm 2 

Second stage 

~1J/800nm, 1Hz 

φ40 

68



Arrangement for multi-100TW laser 

50J/527nm 

Pump laser 

50J/527nm 

pump laser 

CW 532nm 

pump laser 

fs oscillator 

500mW/20fs 

Offern 

Stretcher 

3J/532nm/1Hz 

Amplifier II 

Amplifier I 

500mJ/10Hz 

532nm SF Laser 

1m 

Final amplifier 

~30J/800nm/20min 

600mJ/30fs 

~20TW 

Compressor I Target 

Chamber I 

Area for power supply, 1X6 meters Control Platform 

Room size: 

14X8 meters 

Compressor II 

Pre-pulse 

Generator 

20J/40fs 

~500TW 

Target 

Chamber II 

Door 

Clear 

door 69



Doubled trip stretcher 

70

71 

Calculation on the stretcher dispersion 

2 

2 

2 

3 

0 

0 ) 

sin 

( 

1 

' 

2 

/ 

2 

68 

. 

7 

' 

' 

) 

2 

ln 

4 

( 

γ 

λ 

π 

λ 

− 

− 

− 

• 

= 

Φ 

= 

d 

L 

R 

d 

c 

t 

t 

t out 

Phase and pulse duration 

after stretcher 

) 

sin( 

sin 

) 

sin 

sin 

( 

2 

)) 

cos( 

arcsin( 

) 

sin( 

sin 

) 

sin 

sin 

( 

) 

sin( 

sin 

) 

sin 

sin 

( 

sin 

) 

sin( 

sin 

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sin( 

2 

sin 

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sin( 

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5 

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5 

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5 

0 

5 

5 

4 

5 

0 

0 

5 

4 

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2 

3 

1 

2 

1 

θ 

θ 

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θ 

θ 

λ 

θ 

θ 

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θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

θ 

ω 

ω 

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+ 

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+ 

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+ 

+ 

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数理学部实验物理讲习班



72



Nd:YAG laser 

5ns/0.1J/532nm 

DG535 

Ti:S laser 

20fs/5nJ/800nm 

E-O Gate 

Stretcher: 0.6ns 

Design and experiment of OPCPA 

100mJ 

Telescopy×0.18 


0.4J 

Delay Dealy 


DM1 DM2 DM3 DM4 

LBO 

OPAI 

After OPAI 

~60μJ 

Telescope×3.8 

LBO 

OPAII 

compressor 

Problems: 1.Stable single frequency operation 

2.High energy necessary because of low efficiency 

? 

800nm 

73



A new design with high efficiency 

Mode-Locking 

Nd:YVO4 laser, 100nJ 

500ps/1064nm/80MHz 

PLL Circuit for 

synchronized ps 

and fs laser 

Circuit for control 

cavity length 

Ti:S laser,5nJ 

20fs/800nm/80MHz 

under construction 

Regenerative 

amplifier pump 

with DL 

TV-Rb clock 

10MHz 

stretcher~ 500ps 

2mJ 

1kHz 

PC Dazzler 

Multi 

pass amp 

100mJ 

10Hz 

SHG 

50mJ 

532nm 

2mJ/10Hz 

800nm 

74



M 1 

LD pumped actively mode-locking 

PZT 

The locked 

phase loop 

circuit 

Nd:YAG AOM OC 

1746mm 

Nd:YAG laser 

pin 

82MHz referred 

frequency 

Diagram of the all solid state 

active-mode locking Nd:YAG 

laser. The frequency is 82MHz 

strength coefficient 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 

-1000 -500 0 500 1000 

d l i ( ) 

The autocorrelation trace 

of mode locked pulse. The 

full width is about 488 psec. 

75



PC1 TFP 

From Stretcher 

λ/2 

MR4 

H 

MR3 

MR7 

Pump: 30mJ/532nm 

Output:~2mJ/800nm 

Regenerative amplifier 

To oscilloscope for monitor 

the amplified train trace From 1kHz pump laser 

PH3 

MP1 MR8 F3 

Ti:S 

PH4 

λ/4 

F1 

F2 

FI2 

MP3 

Glan Prism 

MP2 

MR2 

.H 

MR6 

PIN MR5 To Main Amp 

MR1 

76



Spectrum Shaping Control with AOPDF 

Fa st Axis 

(mode 1) 

Acoustic 

wave 

Slow Axis (mode 2) 

Acoustic-Optic Programmable Dispersive Filter for spectral 

amplitude and phase control 

77



Spectra with shaping technique 

Seeding pulse 

Amplified pulse without 

AOPDF work 

Amplified pulse with 

AOPDF work 

78



Multi-pass amplifier 

From Reg. 

1Hz Nd:YAG 

2.6J@532nm 

Glan prism 

PC 3 PC 4 

Glan prism 

With 2.6J pump laser energy, amplified laser of 700mJ 

was obtained, corresponding to the efficiency of 27% 

λ/2 

79



Layout of 100J pump laser system 

80



81



~ 

0.2 

7米 

~ 

0.2 0.1 

1 

米 

~ 

0.3 

9米 

IR5 

MP1 

M7 

M4 

M11 

IR2 

晶体φ85×20mm 

MP3 

MP7 

MP2 

MP6 

M3 

M8 

M12 

IR4 

Design of final amplifier 

~2.16米 

MP4 

MP5 

PC 

The lower efficiency of amplification infer to the possible ASE 82 

IR3 

~2.6米 

~2.0米 

~2.16米 

M10 

 

Pumped the final amplifier with 80J laser at 527nm, laser 

energy only 5J was obtained at initial experiment. 

M9 

M2 

MP9 

M6 

MP10 

M5 

~ ~ 

0.5 0.6 

米米 

~ 

0.7 

米



Eliminate ASE and PL with index match material 

Transverse Gain 

10 5 

10 4 

10 3 

10 2 

10 1 

3 

4 5 

Beam Diameter /cm 

N = N = 1.76 N = N = 1 

1 Ti: sapphire 2 air 

( N − N ) 

= = 7.6% = 1/ = 13 

R 

2 

1 2 

2 

( N1+ N2) 

G R 

Using thermoplastic (Cargille Laboratories, Inc.) material 

can well eliminate the effect. 

Amplified energy of 20J was obtained finally 

6 

7 

8 

83



Layout of vacuum compressor 

Vacuum pumps 

Space size of the chamber:900×700mm, 

Incident angle: 24 degree,diffractive angle: 51degree 

84



85



Gratings of compressor 

86



The record works on TW laser 

The highest peak power—850W 

JAERI, Japan, K.Yamakawa et al, 

The highest power density— 0.8X1022W/cm2 Michigan University, USA, S.Bahk et al, CLEO2004 

The highest peak power from OPCPA—500TW 

Institute of Applied Physics, Russian 

The highest contrast ratio— 10-11 French, USA (Michigan PW) 

The shortest pulse duration— 1TW/10fs,10TW/12fs 

AIST Japan, H.Takada et al 

87



88



Optimize CPA laser with new techniques 

Improved beam quality for higher focusable intensity 

correct wave-front distortion, adaptive optics system. 

Spectrum shaping for shorter pulse duration 

SLM (spatial liquid crystal modulator) 

Acoustic-optics modulator 

Phase controlling for stronger nonlinear interaction 

Carrier Envelope Phase control. 

Eliminate the ASE for a higher contrast ratio. 

Spatial filter, Pockels Cells. 

OPCPA-Optical Parametric Chirped Pulse Amplification 

DCPA,Absorber 

Contrast ratio: 10 

89 

-10 ~10-11 CLEO: 2005



Outline 




Amplification 


Summary 

90



91



Compression laser pulse to 5fs 

1kHz amplifier 

Femtolaser Inc 

25 fs 

1.8 mJ 

Ag mirror Chirped 

mirror 

Ne gas 

Wedge pair 

Chirped 

mirror 

5 - 7 fs 

0.9 mJ 

Ag mirror Ag mirror 

92



Generation of attosecond HHG X ray laser 

Drescher et al. Science 291 1923 (2001) 

93



Generation of fs sub-harmonic waves 

Harmonic Wave 

Order 

Waves Relation 

Wavelength (nm) 

Pulse Duration 

(fs) 

Single Max 

Power (mW) 

Multi-Waves 

Power (mW) 

Multi-Waves 

Power (mW) 

ω 

2580 

2ω 

Cr:Mg2 SiO4 1290 

20 

500 

200 

100 

3ω 

Ti:Al2 O3 860 

10 

1000 

400 

200 

4ω 

2ω + 

2ω 

645 

50 

200 

200 

100 

5ω 

3ω + 

2ω 

516 

50 

300 

300 

300 

6ω 

3ω 

+3ω 

430 

20 

400 

400 

200 

7ω 

3ω 

+4ω 

2ω 

+5ω 

370 

80 

100 

100 

8ω 

2ω 

+6ω 

3ω 

+5ω 

323 

80 

200 

100 

94



Coherent synthesization for sub-fs pulse 

1200nm 

2ω 

800nm 

3ω 

600nm 

4ω 

480nm 

5ω 

400nm 

6ω 

Assump the duration is 5fs for each pulse, 

the coherent synthesization will lead to sub-1fs 

laser pulse. 

95



Summary 

Novel 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 feasiable new 

way to generate femtosecond laser pulse by sum 

frequency was proposed 

96



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. 

97



Acknowledgement for Collaborators 

Jie Zhang, Professor of IOP 

Staffs: 

Prof Yuxin Nie, Naicheng Shen, 

Dr Hao Teng, Mr Dehua Li, Prof Zhiguo Zhang 

Post-doctor, 

Zhaohua Wang, Qiang Du 

Graduated 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 

98



Thank You for your attention! 

99

飞秒激光产生与控制

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