Recent Status of “玄武 (GENBU) ”- - Main Laser -

J. Kawanaka Institute of Laser Engineering (ILE), Osaka University

HEC-DPSSL 2009 Dresden, Germany June 10, 2009 ILE / Osaka Outline

1. Milestone of Reactor Driver ・ Pulse energy and repetition rate

2. “玄武 (GENBU)” - Laser -conceptual design - ・ 1-kJ system with cryogenic Yb:YAG ・ Industrial applications with high-power ・ New technologies - Cryogenic Yb:YAG, L-size Active-Mirror, BB-OPCPA - 3. Status o f Fiber O scill ator ・ Front end of “GENBU” - Laser

4. “GENBU-Kid” - Laser ・ ”GENBU-Kid”-laser with 2 J, 100 Hz for feasibility studies 1. Milestone of Reactor Driver

LFEX Laser and GEKKO XII IFE laser history

Single Shot 100M 10M Research 101.05 μm NIF Helios 0.53 μm * Flash-lamp-pump LMJ 1M 0.35 μm 10M * Nd:glass Av DEMO

ILE e Omega FIREX-II rage Po 100k EP （ ） 1M Omega ILE LFER

Shiva TERA w

rgy (J) 10k 100k er (W er Argus Gekko XII （ILE） FIREX-I （ILE） Repeatable 1k VENUS 10k Cyclops @ （ ） Reactor

ulse Ene Gekko MII ILE

（阪大） 10Hz) PP Janus Gekko IV Gekko II （ILE） * DPSSL 100 * Crystal or Ceramics 1k

Mercury 10 100 HALNA （ILE） LUCIA 1 10 1970 1980 1990 2000 2010 2020 2030 2040

Year Diode-pumped solid-state lasers (DPSSL)

KOYO-F Reactor CryogenicNd:glass Yb:YAG laser ceramics Fast Ignition LSifitiLaser Specification Implosion Implosion Heating Pulse Energy 1.1 MJ 0.1 MJ Wavelength 343 nm(3w) ~ 1030 nm Fast Heating Rep. Rate 16 Hz Plug to Laser Eff. > 10% Beam Number 32 1 System DPSSL OPCPA Ignition / Burn

→ 1-um DPSSL produces huge pulse energy. 1 kJ system is a milestone of the reactor driver

Module Yb:YAG Cryogenic AtiActive Mi rror LD Tower ・Cryogenic End Plate Yb:YAG ceramics Mirror

・Active Mirror

Input 15 m Amplified 64kJ (1ω) /module Pulse Pulse 38kJ (3ω)/) /mod u le

8 x 8 Seggyment Array

8 m 10 x 10 x t1.5 cm 081at%0.81 at. % Milestone 1kJ / segment of the reactor driver ! Current status of pulse lasers and the next generation of high- power-laser applications

NIF, LMJ Compression laser 1M Laser Fusion Heating laser 100K FIREX-II Laser Rocket GEKKO XII Debris Remove 10K LFEX

gy (J) Laser Lightening kJ,,p ps rr 1K PW-Laser 1 kW Source100Hz

100 Mercury PW lse Ene uu Polaris HALNA CThCancer Therapy P 10 Commercial ns (FL) PET ps EUV-Laser 1 Commercial fs (DPSSL) EUV-L 0.1 10-4 10-3 10-2 10-1 1 10 102 103 104 105

Repetition Rate (Hz) 2. “玄武 (GENBU)” - Laser -conceptlditual design -

Ancient wall painting of “GENBU” （An old tomb of “KITORA”, “GENBU” is the god for the north.） Block diagram of “GENBU (玄武) ” - laser (Generation of ENergetic Beam Ultimate)

Cryogenic Yb:YAG Ceramics Feasibility study should be done. Active Mirror Architecture Main Laser

1st 2nd E = 1 kJ Front End PlPulse Amplifier Amplifier Pulse Δt = 10 - 100 ps (Fiber Laser) Stretcher （Cryogenic （Cryogenic Compressor f = 50 -100 Hz Yb:YAG） Yb:YAG） λ = 1030 nm Puuselse Compressor E=75J Δt=20ps 2nd f = 100 Hz Harmonics λ = 515nm E=30J Δt = 5 fs~8 ps (Variable)

White Light Pulse OPCPA Pulse Ppeak = 0.04~6 PW Generation Stretcher (3-stage) Compressor f = 100 Hz

l0 = 1030 nm OPCPA Laser Δλ = 600 nm OPCPA over 600 nm Main Laser of “玄武 GENBU” - Laser

Fiber system

fs - Fiber Fiber Fiber Pulse Picker Oscillator Stretcher Amplifier

Δt=30fs Δt=1.1ns Δt = 90ps E=3nJ E=2nJ E = 2 mJ Rep. Rate = 20 MHz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep.Rate ~ 100 Hz

Cryogenic Yb:YAG system

Grating Pair Pre-Ampl Main Grating Pair Stretcher ifier Amplifier Compressor

Δt = 3ns Δt = 1ns Δt = 20ps E=1mJ E=2J E=200 J E = 100 J Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz φ =3mm

（~1kJ） GENBU-Kid E=2kJ 1-kJ GENBU Main Amplifier Head

Cryogenic Yb:YAG Ceramics Active Mirror ・ Controlled stimulated emission cross ・ Good spatial mode coupling section ・ Easy power scaling ・ Improved thermal conductivity ・ Double pass amplification a reflection ・ Reduced re-absorption in quasi-3-level ・ Simplified optical layout

But to realize this laser arrangement we have many technical issues to address. System layout and schedule

12m 4m Oscillator Pulse 1kJ-Laser Stretcher Application 1kJ Cham ber Active Mirror Amplifier Pulse (Cryogenic Yb:YAG) Compressor 100J Amp. 6m

Pulse Pulse Compressor Ultra Short Compressor OPCPA Pulse Laser Application Chamber

3-years 3. Status of Fiber Oscillator

Ancient wall painting of “GENBU” （An old tomb of “KITORA”, “GENBU” is the god for the north.） Main Laser of “玄武 GENBU” - Laser

Fiber system

fs - Fiber Fiber Fiber Pulse Picker Oscillator Stretcher Amplifier

Δt=30fs Δt=1.1ns Δt = 90ps E=3nJ E=2nJ E = 2 mJ Rep. Rate = 20 MHz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep.Rate ~ 100 Hz

Cryogenic Yb:YAG system

Grating Pair Pre- Main Grating Pair Stretcher Amplifier Amplifier Compressor

Δt = 3ns Δt = 1ns Δt = 20ps E=1mJ E=2J E=200 J E = 100 J Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz Rep. Rate ~ 100 Hz φ =3mm

（~1kJ） E=2kJ Cryogenic mode-locked Yb Fiber Laser Pulse Train Beam Profile

RT LN2 Mode-locked Spectra I

R.T. Mode-locked Spectra II

R.T.

Grating 300 mm/lines Æ 600mm/lines Pulse Width

R.T.

450 fs (sech2) 4. “GENBU - Kid” - Laser

Pre-amplifier of “GENBU” – Laser (2J, 100Hz) Block diagram of “GENBU (玄武) ” - laser (Generation of ENergetic Beam Ultimate)

Cryogenic Yb:YAG Ceramics Feasibility study should be done. Active Mirror Architecture Main Laser

1st 2nd E = 1 kJ Front End PlPulse Amplifier Amplifier Pulse Δt = 10 - 100 ps (Fiber Laser) Stretcher （Cryogenic （Cryogenic Compressor f = 50 -100 Hz Yb:YAG） Yb:YAG） λ = 1030 nm Puuselse Compressor E=75J Δt=20ps 2nd f = 100 Hz Harmonics λ = 515nm E=30J Δt = 5 fs~8 ps (Variable)

White Light Pulse OPCPA Pulse Ppeak = 0.04~6 PW Generation Stretcher (3-stage) Compressor f = 100 Hz

l0 = 1030 nm OPCPA Laser Δλ = 600 nm OPCPA over 600 nm Cryogenic Yb:YAG as an amplifier material

Advantages 1. Wide Tunability of Stimulated Emission Cross Section 2. Improved Thermal Strength Thermal conductivity κ, Thermal expanstion 1/L(dL/dT), Thermal refrative index dn/dT 3. Efficient Laser Operation without Re-absorption

1000 1 at. % 5 at. % m K)m K) //// 300 10 at. % 25 at. %

100

onductivity (W (W onductivity onductivity 30

10 Thermal C C Thermal Thermal 3 310 30 100 300 Temperature (K)

J. Kawanaka, S. Tokita, H. Nishioka, M. Fujita, K. Yamakawa, K. Ueda and Y. Izawa,” Laser Physics 15, pp. 1306-1312 (2005). Total-Reflection Active Mirror (TRAM)

No spatial overlap of input and 60mm output pulses on the surface ensures Thick Yb:YAG due to ・Avoid damage threshold reduction improved κ at low T due to interference. 18mm allows Brewster angle with no coating ・Simp le pump ing w ith jus t 1-or realizes 60mm 2- passes. ・Less cost YAG Pump Seed pulse Yb:YAG 20 at.% t = 400μm Liquid Nitrogen

Total reflection with no coating Direct cooling with liquid nitrogen ensures realizes ・Less temperature rise . ・Less temperature rise ・Efficient hydrodynamic cooling 1J x 100Hz laser system as a test bench of pre-amp. of “GENBU” “GENBU – Kid”

CW Fiber Oscillator & 10ns, pJ-class J-class Pulse Slicer 4-pass Amplifier

Regenerative Amplifier Yb:YAG Rod φ12×6.6mm 5 at. % mJ-class

TRAM TRAM is under preparation. Rod was used. Regenerative Amplifier – Feasibility study of TRAM Laser -

Seed

TFP Amplified PPockelsockels cell FR LD focusing λ/4 λ/4 optics

TFP

Cavity length = 6.6 m Cryygogenic Compact size = 1.6m x 0.5m Yb:YAG No. of round trips = ~20 TRAM I = 3.4 kW/cm2 @700μs (2.4 J/cm2)

G0 = 445/pass.5/pass Cavity loss/round trip = 0.15 Regenerative Amplifier – Feasibility of TRAM Laser -

10 30 9 E = 6.5 mJ @@p14th round trip 25 8 ηo-o = 9.3% Roun 7 20 [mJ] d yy

6 (time trip 5 15 4 lse energ s

uu 10 3 ) P 2 Pump : 70 mJ 5 1 (100W, 700μs) 0 0 10 100 1000

Repetition (Hz) 4 - pass amplifier for 2 J, 100 Hz.

Fiber-Coupled Laser Diodes Two diode units are used for pump. The output power is 2.5 kW and the duration is varied below 2 ms at a rep. rate of 100 Hz. The fiber core is φ1mm.

.) 151.5 bb 1.0 0.5 ntensity (ar

I 0.0 -3 -2 -1 0 1 2 3 Horizontal axis (mm)

Laser Head φ12×6.6mm, 5 at. % Yb:YAG rod mounted between two copper plates and hldheld inavacuum and cooldled to cryogenic temperatures. The copper plate has a φ6 mm hole for the laser pass. Output pulse energy and temporal waveform at 100Hz

160 160 E = 150 mJ ηo-o = 30% 700 μs 140 300 μs 140 mJ) (mJ)

200 μs (( 120 120 100 100 ηslope = 48% 80 100 μs 80 lse energy lse energy lse energy lse energy uu 60 uu 60 010.1001msμs 0.2ms200μs 40 40 0.3ms300μs

Output p 20 0.7ms700μs

Output p 20 0 0 0 1000 2000 3000 4000 00.51 LD peak power (W) Diode emission energy (J) 1.2 ) ss 1 0.8 G0 = 13/pass 2 @700μs 2 0.6 I = 7.8 kW/cm (5.5 J/cm ) al (Arb.Unit 8ns8 ns nn 0.4 Transmission loss = 0.3/pass 0.2 0 We need more TRAMs for higher alized Sig mm -020.2 pulse energy. Nor 1050 1150 1250 1350 Pump source is enough high for 1 J. time (ns) Summary

・ Femtosecond fiber oscillator is under development. 450fs, 33 MHz, ?? nJ ・ Cryogenic Yb:YAG ceramics and active mirror architecture have been focused on for our concept design of “玄武(GENBU)”- laser, especially main laser.. ・ Our original TRAM (Total-Reflection Active- Mirror) was used in the regenerative amplifier for feasibility study with these two new technologies. E = 6.5 mJ @ 200 Hz, 2 mJ @ 1kHz

ηo-o = 9.3% 2 2 G0 = 4.5 @ I = 3.4 kW/cm @700μs (2.4 J/cm ) ・ Sub-joule pulse energy has been demonstrated with a cryogenic Yb:YAG rod. E = 150 mJ @ 100Hz

ηo-o = 30% ηslope = 48% 2 2 G0 = 13 @ I = 7.8 kW/cm @700μs (5.5 J/cm ) ・ Three TRAMs will be used instead of the rod for 1 J, 100 Hz demo in 4-pass amp. ⇒ (2008~2009) ⇒ (2010) CPA demo. for ps-pulses Collaborators on “玄武 ” - project

K. YAMAKAWA N. MIYANAGA M. AOYAMA H. FUJITA Y. AKAHANE H. YOSHIDA Y. F U J I M O TO R. YASUHARA S. J. PEAECE T. KAWASHIMA Y. TAKEUCHI R. KATAI A. YOSHIDA H. KAN Y. YA S U N O

H. FURUSE

T. YANAGITANI

F. YAMAMURA High-Power-Laser Research Committee

Chair ILE/Osaka Univ. Y. Izawa JST Satellite Miyazaki K. Kurosawa Sumitomo Ele. Ind., LTD K. Ehata AIST Y. Owadano SOC F. Yamamura ILT M. FujitaUniv. Konoshima Chem. Co, LTD GSCNPI K. Fujita T. Yanagitani UiUniv. Hyogo TMT. Mochi zu ki Hamamatsu Photonics K. K. JAEA K. Yamakawa T. Kawashima ILS/UEC K. Ueda NEC Y. Suzuki Fukui Univ . T. Kanabe Mitsubishi Heavy Ind., LTD Kyoto Univ. S. Sakabe Y. So m a n Kinki Univ. H. Nakano Unitac Co. T. Takahashi M. Yoshida Nissin Ele. Co., LTD K. Tanaka ILE/Osaka Univ. N. Miyanaga M. Nakatsuka N. Sarukura Mitsubishi Electric Co. J. Nishimae T. Jitsuno JAST Y. Hatsuda JKJ. Kawana ka Paradigm Laser Res. K. Washio K. Tsubakimoto Shin-etsu quartz Pro. Co. LTD A. Fujinoki