zhiyi wei, h.han, p.wang, j.tian, w.ling, z.wang, j.zhang nov. 23~25, 2005. beijing phase control,...
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Zhiyi WEI, H.HAN, P.Wang, J.Tian,
W.Ling, Z.Wang, J.Zhang
Nov. 23~25, 2005. Beijing
Phase control, synchronization and amplification of femtosecond Ti:sapphire laser
Institute of Physics, CAS, Beijing 100080, China
Sino-Germany Symposium on Quantum Engineering
Outline
Background and motivation
Phase control femtosecond laser
Synchronized femtosecond laser
Amplification of femtosecond laser
Summary and Acknowledgement
Background and motivation
Phase control femtosecond laser
Synchronized femtosecond laser
Amplification of femtosecond laser
Summary and Acknowledgement
Background
Laser- original from the optical quantum theory by Einstein. Laser- a kind of electric-magnetic wave. E(,t)=A(t/)cos (t+)
AA: Amplitude, Energy depend on fund: Amplitude, Energy depend on fund ccwavelength, 1nm was obtawavelength, 1nm was obtained with attosecond laser pulse.ined with attosecond laser pulse. controllable with femtosecond lasecontrollable with femtosecond laserr ,,pulse durationpulse duration
play a key role in laser development
Pursue the shortest pulse is a challenge work
Applications of Ultrashort Laser Pulse
Ultrashort laser
Attosecond Physics Ultrafast electronics, optical communication
High field physics, laser acceleration etc.,
Ultrafast phenomena
Femtosecond micro/nano fabrication
THz radiation
Frequency omb,Optical clock
UL——The key for seeking answer
Nobel Prizes
Pushing laser intensity
Pursue the highest laser intensity is another challenge work, the discover of Chirped Pulse Amplification lead to the revolutionary progress in power density.
I=E/E: energy : pulse duration: beam size
Ultrafast and Ultrastrong laser It is another challenge work to pursue high power laser.
Recent development of CPA laser
Facility Peak Power Type Pulse duration Pulse Energy
RAL,UK 1PW Nd:glass/OPCPA 600fs 600J
ILE,Japan 700TW Nd:glass/OPCPA 700fs 350J
JAERI,Japan 850TW Ti:sapphire 33fs 28J
MBI,Germany 100TW Ti:sapphire 50fs 5J
Phelix,Germany 1PW Ti:s/Nd:glass 500 fs 500 J
LLNL,USA 200TW Ti:sapphire 100fs 20J
LULI,France 100TW Nd:glass 300fs 30J
CEDEX,France 100TW Ti:sapphire 25fs 2.5J
QG-II,China 120TW Ti:sapphire 36fs 4.2J
SILEX-1, China 286TW Ti:sapphire 30fs 8.6J
Multi-100TW facilities are available in many labs in the world now.Some new facilities are under constructing
全世界最高聚焦功率密度激光
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, CLEO2004The highest peak power from OPCAP—100TW Russian, ALT05, Tianjin ChinaThe highest contrast ratio— 10-11
French, USA (Michigan PW) The shortest pulse duration— 1TW/10fs,10TW/12fs AIST Japan, H.Takada et al
Motivation of this talk
laser1
laser2 Laser N
1. Limitation Because of the limited crystal size and optical damage threshold, it has a Bottle Neck effect on the increasing of laser peak power.2. A new way toward higher intensity Phase controlled and synchronized n femtosecond ultra-strong lasers, it will enable us to generate an un-precedent power density of n2I.
Phase Controlled5-fs, 100 MHz
Ti:Sapphire Laser
Highly Energy Stable Multi-pass Amplifier
30 fs
Pulse Stretcher(negative Chirp)
Material Compression
10 kHz, 1 mJ30 fs
Phase Control+
Puls Selector
Hollow Fiber Comp.
10 kHz, 0.5 mJ, 5 fsPhase Controlled
A. Baltuska, et al., Nature, 421, 611 (2003)
Diagram show on CEP controlled CPA
Pow er am plifier
gas target
H igh-pass filter
Vacuum
Q uasi-m onocycle“cos” driver laser fie ld
Bandpass m irror
Isolated attosecond XUV pulse
cw pum plaser
Detector of fastCEP drift
Detector of slowCEP drift
AO M
Phase-lockingelectronics
Pum p laser
Ti:Sa oscillator Stretcher Com pressor
-15 -10 -5 0 5 10-1
0
1
-20 -10 0 10 20
0
8
A(t) =/2=0
Ele
ctri
c fi
eld
str
eng
th (
a.u
.)
Time (fs)
Inte
nsi
ty
Delay (fs)
1.5 2.00
1
Photon energy (eV)
Inte
nsi
ty
1000 800 600
Wavelength (nm)
Output of a 0.1-TW CEP-stabilized
Ti:sapphire system in Vienna
Laser for attosecond generation
Background and motivation
Phase control femtosecond laser
Synchronized femtosecond laser
Amplification of femtosecond laser
Summary and Acknowledgement
Outline
Stable femtosecond Ti:sapphire oscillator
Stability <1%Average power >1WPulse duration 15 ~ 30fsPeak Power ~1MWTunable range 760nm~850nmRepetition rate 50 ~ 100MHz
600mm
200mm
Pulse 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
Powe
r(a.u
)
Running Time (hour)
<20fs
2.3 fs
Progress on Ultrashort Laser Pulses
Toward Monocycles pulse (<3fs in visible range )
L.Xu et al., Opt Lett, 21, 2008 (1996)
Carrier-envelope phase (CEP)
Principle of carrier envelop phase control
Carrier-envelope -phase (CEP)
Carrier-envelope offset frequency fceo
f =nf
rep
2(nfrep
nfrep
nfrep
f=2(nfrep nfrep
Self-reference technique
Stabilizing laser cavity length for locking frep
Modulating pump power for locking
Layout of experiment for CEP controlantenna
TV-Rb clcok10MHz
PLL
for frep
PLL
for CE
P
PCF
Grating
Beat frequency
0 50 100 150 200 250 300 3500
10
20
30
40
50
60
70
80
90
Locking
RF
fr
eq
ue
ncy(M
Hz)
Time(s)
Without Locking
fceo
frep
0 50 100 150 200 250 300 350
6
8
10
12
14
16
18
20
RF
fr
eque
ncy(
MH
z)
Time(s)
Without locking
Locking
Locking of CE phase with TV- Rb clock
f2=+nfrep f1=+mfrep
frep frep
f
I (f)
fDFG= (m-n)frep DFG: 627-1000nm1680nm()
Free CE phase, f1 = nfrep
SHG: 1680nm 840nm(2)
CEP locked, f2 = 2nfrep
DFG: Difference frequency generation: fDFG= f1 -f2= (+mfrep)-(+nfrep)= (m-n)frep
Stabilized CE phase with DFG technique
DFG of the ultra-broaden band laser spectrum will generate a self-stabilized femtosecond frequency comb at wavelength around 1.5micrometer, it will be free of the electronics control for frequency beat.M. Zimmermann et al., MPQ; T. Fuji et al., TUW; S. M. Foreman et al., JILA&MIT
OC T=10%
f=10 cm M1 M2
Ti:sa
M3
5W 532nmMillennia
600 700 800 900 1000 1100
10
100
1000
Inte
nsi
ty
wavelength(nm)
T=10%
The spectrum support pulse duration of less than 7fs
M1-M3: Chirped mirror
Cavity length 85 cm (F 170 MHz)
Ultra-broaden bandwidth fs laser
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
The latest result of spectrum
Directly output from the oscillator, covered from 550~1050nm
Outline
Background and motivation
Phase control femtosecond laser
Synchronized femtosecond laser
Amplification of femtosecond laser
Summary and Acknowledgement
Opt Lett, Vol.26,1806 (2001), Opt Lett, Vol.26,1806 (2001), Appl Phys B, Vol74.S171, (2002)Appl Phys B, Vol74.S171, (2002)
12
8
4
0
Inte
nsity
of
SF
G
543210Time (second)
S -P M illen n ia X s
S -P T -4 0 Z -1 0 6 C
P 1
R G
P 3
M 5
H R
P Z TP 2
P 4
M 1
P D
M 4
M 6
M 3M 2
T 1
C r:F
M 7 S E S A M
T 2
Ti:S
P D
To A C an d C C
P Z T D riv e r
F 2F 1
Ti:sapphire laser 600mW/18fs/820nm
Cr:forsterite laser
200mW/42fs/1300nm
For the first time the synchronization based on different gain media was demonstrated, the timing jitter is less than 1fs.
First synchronization between two different femtosecond lasers
Robust synchronization based on the improved design
Average power:>1W Pulse duration: 30 ~ 70fs Tunable range: 730 ~ 850nm Timing jitter: <400a Unstability: <1 % Tolerance of mismatch of cavity length: >10mm
Measurement of SFG and timing jitter
0.0 0.5 1.0 1.5 2.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.0 0.5 1.0 1.5 2.00.48
0.49
0.50
0.51
0.52
Inte
nsity
(a.
u.)
Time (s)
Nor
mal
ized
inte
nsity
Time (s)
V = 0.5Vstandard = 0.00653 t
I(t)
K
Timing jitter
V/V
SFG
j
V
VK
~
The cross-correlation trace (SFG) and its fluctuation at half amplitude. The fluctuation is proportional to timing jitter and was measured within 5s, it shows the timing jitter is less than 400as.
J.Tian et al; Opt Lett., Vol.30, 2161(2005)
Measurement of CEP between two lasers
0 20 40 60 80 100 120
-70
-60
-50
-40
-30
-20
-10
0
frep
frep+
Beat frequencyCentral frequency: 78.75 MHzSpan: 150 MHzResolution:100 KHzSweep time: 50 ms
inte
nsit
y (d
Bm
)
frequency (MHz)
frep-
frep : Repetition rate,
90MHz : ~28MHzS/N : 41dB
f1=1+nfrep
f2=2+nfrep
f1- f2 1- 2
1 2
frep frep
f2=2+mfrep f1=1+nfrep
f
I (f)
frep
1
2
Considering the coupling inside the medium, each laser will suffer the frequency shift. For laser 2:
)exp(8 2
12
122 ddST
LPn
]})(exp[]{exp[4 22
12
122 ddST
LPn
Induced frequency shift
laser1
laser2
Coupling area
Medium for XPM
Where: P1 : Intra-cavity peak power of laser 1
2 : The central wavelength of laser 2
S : The interaction area L : The effective interaction length T1 : Pulse of pulse duration
= 2c(1-2)/(T102)
The walk off parameter
for Vg1 = Vg2
for Vg1 Vg2
-3 -2 -1 0 1 2 3 4 5 6 7-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Ind
uce
d f
req
uen
cy s
hif
t Initial normalized time delay
Vg1 箎 Vg2
Vg1=Vg2
Induced-frequency shift as the function of the normalized initial delay of both the lasers
dd
T
GVDP
T
GVDP
S
LnT
21
12
12
2128
Build up time of synchronization
So the time to reach synchronization is:
/]1)1[( NdNT
fT d
offT
1
β1log0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
-4-3-2-10123456
wav
elen
gth
shift
(nm
)Round trip times
wavelength shift of front laser wavelength shift of hind laser
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000.00
0.05
0.10
0.15
0.20
0.25
0.30
Nor
mal
ized
del
ay
delay between both pulses
From the frequency shift, it is possible to deduce the relative time delay between two closer pulses:
Here <0, after N times round trip inside cavity, the new delay time will be:
The time interval and accumulated wavelength shift of both lasers versus round trip times cross in the crystal.
12
12
22
2
12
21
21
1
2
2
r
GVDGVD
T
c
r
GVDGVD
T
c
And wavelengths shift is
Actively synchronization between picosecond and femtosecond lasers
ps laser : central wavelength 1064nm ; 7ps ; output >1W 。 fs laser : central wavelength 810nm ; ~50fs ; output >600mW
ps laser
cavity controller
fslaser
86MHz
816MHzPLL
BBO
PLL
Adjustable delay
DetectorSFG
Before synchronization
Aftersynchronization
1064nm 810nm 532nm 460nm 405nm
Sum frequency generation between fs and ps laser
445 450 455 460 465 470 475 4800
500
1000
1500
2000
2500
3000
3500
4000
理 论 曲 线 实 测 曲 线
(a.u.)
强度
( nm)波 长
Spectrum of SFG laser
Theory: 7.1nm
Experiment: 5.5nm
Outline
Background and motivation
Phase control femtosecond laser
Synchronized femtosecond laser
Amplification of femtosecond laser
Summary and Acknowledgement
Development of TW laser at IoP Beijing
Extreme Light I (in 1999 ) Pulse energy : 36mJ Pulse duration : 25fs Peak power : 1.4TW
Extreme Light II ( in 2001 ) Pulse energy : 640mJ Pulse duration : 31fs Peak power : ~20TW
New design and system of 20TW peak power with two modes
Pro-350-101.4J/532nm/10Hz
AOPDF
Vacuum compressor
Evolu
tion 20
527nm
/1kH
z
1 kH
z pre-
amp
lifier
Main amplifier
Verdi-10 1W/fs oscillatorÖffern stretcher
Pro-350-101.4J/532nm/10Hz
Space2×4.5m
Two output with two repetition rate2mJ/990Hz; 20TW/10Hz
Construction of multi-100TW laser system
500 mJ/ 532nm/10HzSingle frequency laser
CEP controlled oscillator20fs/5nJ/80MHz
OPCPA, 2mJ/10 Hz
Finial main amplifier15 J, 1Hz( or single shot)
Second main amplifier~1J, 1Hz
comprerssor8J/40fs/200TW
3J /532nm/1Hz or800mJ/532nm/10Hz
~50J/ 527nm pump laserSingle shot (~20min) 1Hz
Strtetcher>600ps
Adaptive optical system1×1021
1nJ
2106
14/3J
160
40
500MW/cm27/0.8J
14/7
50
Jp = 2J/cm2
Jp = 2J/cm2
200mJ/cm2
50J/527nm pump laser
Am
plifier II
Am
plifier IOffern Strectcher
1.5J/532nm/10H
z
CW
532
nmpu
mp
lase
r
fs o
scill
ator
500m
W/ 2
0fs
8J/40fs/800nm
~200T
W
Target Chamber II
Pre-pulseGenerator
600mJ/30fs/
~20TW
/800nm
Target Chamber I
Final amplifier~15J/800nm/20min
1mArea for power supply, 1X6 meters Control Platform
Door
Clear door
Room size:14X8 meters
Compressor I
40J/527nmPump laser
1.5J/532nm/10H
z
500m
J/10
Hz
532n
m S
F L
aser
Compressor II
Arrangement of lab for multi-100TW laser
Layout of 50J pump laser
~ 0.2 米
~ 2.6 米
MP1 晶体 85×20mm
IR5
IR4
IR3
IR2
MP2
MP3
MP4
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
~ 0.3 9 米
0.1 1
~ 0.2 7 米
PC
箎箎 箎
Design of main amplifier
~ 20
1650
A
10
1650
B
Artificial Ti:S crystal shape for eliminating ASE
Ti:sapphire: Dia 85mmPatent design
Space size of the chamber : 900×700mm,Incident angle: 24 degree , diffractive angle: 51degree
Vacuum pumps
Layout of vacuum compressor
-150-120 -90 -60 -30 0 30 60 90 120 150
0.0
0.2
0.4
0.6
0.8
1.0(a)
compressed pulse seed pulse
Inte
nsi
ty(a
.u)
duration(fs)-150 -120 -90 -60 -30 0 30 60 90 120 150
1E-5
1E-4
1E-3
0.01
0.1
1
(b) compressed pulse seed pulse
Inte
nsi
ty(a
.u)
duration(fs)
Same grating groove between stretcher and compressor
(1200/mm)
-150 -120 -90 -60 -30 0 30 60 90 120 150
0.0
0.2
0.4
0.6
0.8
1.0(a)
compressed pulse seed pulse
Inte
nsi
ty(a
.u)
duration(fs)
-150 -120 -90 -60 -30 0 30 60 90 120 1501E-8
1E-7
1E-6
1E-5
1E-4
1E-3
0.01
0.1
1
10
(b) compressed pulse
seed pulse
Inte
nsi
ty(a
.u)
duration(fs)
Calculation of the optimized parameters in compressor
Different grating groove between
stretcher and compressor (1480/mm)
Large grating from JY
Holder for gratings
Summary
A multi-beams CPA laser with CEP control and synchronization was proposed, it will be enable us to obtain n2 times intensity by coherent overlap the laser beams at target. We locked the CE phase of fs oscillator, ultra-broaden bandwidth was realized with chirped mirrors technique, it will be enable us to further lock CE phase with DFG.Robust synchronized femtosecond lasers with timing jitter of sub-400as was demonstrated, tolerance of cavity length mismatch is longer than 10m.New technique for eliminate ASE from large crystal was proposed.
ACKNOWLEDGEMENT
Thanks to Mr.Zhu Jiangfeng( 朱江峰 ) 、 Gao Cunxiao ( 高存孝 ) 、 Zhao Linghui( 赵玲慧 ),Zhao Huan( 赵环 ) 、 Zhang Wei( 张炜 ) 、 Zhao Yanying (赵研英) ,Tong Juanjuan (佟娟娟) and Wang Yanghui (王延辉) for their partly works.Collaboration and technical discussion with Prof W.Zhao (赵卫), Prof.J.Pan (潘建伟) and T.Yang (杨涛)Supports by Prof Nie Yuxin (聂玉昕) , Prof Sheng Naicheng (沈乃澄) and Mr Li Dehua( 李德华 ).
Funds supported by NSFC and Chinese Academy of Sciences are appreciated
Thank You for your attention!
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