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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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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~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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