Isao MATSUSHIMA, Hidehiko YASHIRO, Toshihisa TOMIE
National Institute of Advanced Industrial Science and Technology (AIST) C2 1-1-1, Umezono, Tsukuba, 3058568, Japan
*This study was partly financially supported by the Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and Technology, based on screening and counseling by the Atomic Energy Commission.
Laser system for laser-plasma X-ray source
10 kHz 54 W Ti:sapphire regenerative amplifier as a pumping laser of a laser-plasma X-ray source
Laser-Plasma X-ray Source
Laser-Plasma X-ray Source
X-ray, λ~nm, <nsblight point source
TargetPlasma
High Temperature<100μmϕ,
Ionization >ps,
Laser
>>mJ, ~10μmϕps<τ<ns
>1011 W/cm2
*EUPS; extreme ultraviolet (EUV) excited photoelectron spectroscopy*EUV source for defect inspection of multi-layered mask blanks*EUV lithography*X-ray microscopy of living cells
multi kHz repetition-rate is required for high throughput
Laser-Plasma EVU Source
EUPS4
EUPS; extreme ultraviolet (EUV) excited photoelectron spectroscopyOur Application of Laser-PlasmaOur Application of Laser-Plasma
Novel surface analysisEnergy resolution: better than 0.3 eVSpatial resolution: better than 1 μm
MOPA Ti:S
6
789
1
2
3
4
5
6
789
10
2
Pulse Energy (mJ)
5 6 7 8 91
2 3 4 5 6 7 8 910
Repetition Rate (kHz)
CLIA
Brown U U Tokyo
AIST
AIST
U Deraware
Max-Born
U Colorado
FS-10
Single Stage UncompressSingle Stage Compressed
Multi-Stage CompressedMulti-Stage Uncompress
commercial Ti:S
FiberLaser
Our Target Area
We need Multi-kHz Multi-mJ sub-ps Laser
1. I. Matsushima, H. Yashiro, T. Tomie, “A 37% Efficiency, Kilohertz Repetition Rate Cryogenically Cooled Ti:Sapphire Regenerative Amplifier,” Jpn. J. Appl. Phys. 44, L823-L826 (2005).2. I. Matsushima, H. Yashiro, and T. Tomie, "10 kHz 40 W Ti:sapphire regenerative ring amplifier," Opt. Lett. 31, 2066-2068 (2006).
1
2
Key Technologies
Thermal lensing effect
Symmetric ring resonator
Low loss and high gain
High-quality pump beam
High-average power Ti:Sapphire regenerative amplifierHigh-average power Ti:Sapphire regenerative amplifier
Cryogenic cooling
Good beam quality
High efficiency
Mode-volume matching
f=350mmf=1mM1M2M3M4M5M6λ/ 2PCFIseedAO2/Gf=500mmOUTAO2/GFITi:sap RodTFP
Fig. 1. Schematic drawing of a ring regenerative amplifier. A cryogenic-cooled Ti:sapphire rod is kept in a vacuum cell and placed at the beam waist for f = 1 m intra-cavity lens. M1~ M6 are cavity mirrors; λ/2 is a half-wave plate; PC is a Pockels cell; TFP is a thin film polarizer; FI is a Faraday isolators; and AO2/G is a pump laser.
High-average power Ti:Sapphire regenerative amplifierHigh-average power Ti:Sapphire regenerative amplifier
Pump Laser
AO2/G (PowerLase) ×2
High repetition rate : 10 kHz
High pulse energy : 8mJ x 2
Good beam quality : M2=23.5
for high gain
Cryogenic Cooling
reduce thermal lens
50
40
30
20
10
0
Output Power (W)
180160140120100806040 Pump Power (W)
Output Power before compression
L=3.6m L=3.8m
10 kHz Ti:Sapphire regenerative amplifier10 kHz Ti:Sapphire regenerative amplifier
Fig. 3. Output power of the regenerative amplifier at 10 kHz as a function of pump power.
Output beam quality of 10 kHz regen ampOutput beam quality of 10 kHz regen amp
500μm
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Intensity
-400 -300 -200 -100 0 100 200 300 400 Position (μ )m
Horizontal Vertical
XDL=225μm
2XDL
Focusability: 2XDL >80%Energy⊃
Far field image (56W before compression)
Compressability: 82 fs
Discussion
Scale up to kW?High power pumping green laserCryogenic cooling for kW
un-known non-linear losses at high pumping powerun-known non-linear losses at high pumping power
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Output Fluence Ratio (Experiment/Theory)
180160140120100806040200
Pump Power (W) r060303_18 Graph16
1kHz 3.6m10kHz 3.6m10kHz 3.8m
decrease in conversion efficiency
10kHz Rep-rate Ti:Sap Regen Amp
Summary
10kHz 180W Pump before cpmpression54W outout
2XDL >80%Energy⊃Compressability: 82fs
High average power and pulse energy
Acknowledgments
The liquid nitrogen cryogenic cooling system was designed with advices from AIST Cryogenic Technical Center.
5.4 mJ/pulse
conversion efficiency 30%
The highest output power in the world from a single stage single rod kHz Ti:Sap regen
Scalability to higher output power was discussed.
Requirements of lasers for x-ray generationRequirements of lasers for x-ray generation
Pulse Energy: Multi-mJ
Repetition rate: Multi-kHz
Focusability: a few μm
Minimum pulse duration: 100fs
High-efficiency
Small and simple