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