exaレーザー応用科学 レーザー技術から見た視点 - …...exaレーザー応用科学...
Post on 27-Apr-2020
6 Views
Preview:
TRANSCRIPT
EXAレーザー応用科学
レーザー技術から見た視点
植田憲一 電通大レーザー新世代研究センター
大型レーザー応用科学意見交換会
KTP東京駅日本橋ビジネスセンター
2010年12月16日
コヒーレントビーム結合技術がキーとなる。
インコヒーレント伝送と集光点コヒーレント結合
レーザー技術の基礎としての光学薄膜損傷機構の物理
位相制御位相共役鏡技術
Toward Ultra-high Intensity Lasers
Application of Ceramic Lasers
Introduction of scientific front
Ken-ichi Ueda
Institute for Laser Science
Univ. of Electro-Communications
Chofu, Tokyo, Japan ueda@ils.uec.ac.jp
LCS-6, Muenster, Germany, Dec. 8, 2010
Mode coupling distance
Phase locked multi-beam solid state laser
Solid state laser embedded the gain volume in mode coupling distance.
Active photonic crystal is possible?
N =2,3,4,6
>100, >1000, >10000
Fiber bundle pumping
DKDP OPA
Signal 1 beam 100J/
0.5ns@1100nm
Output 1 beam
@1100nm 4 beam pumping
1ns@527nm
OPA
output
Pump
Focusing spot
Near field
phase profile
Random phase
pumping Wide band DKDP (13% D to H)
Beam combining in OPA (JAERI/ILE Osaka)
Pulse Compression by Backward SRS
K. Ueda, H. Nishioka, K. Kimura, H. Takuma, Advanced Techniques of High Efficiency Pulse
Compression for KrF Lasers, Laser Particle Beams, vol.11, 31-42 (1993).
High-average-power, high-brightness Nd:glass laser
technology (C.B. Dane, L.A. Hackel, LLNL)
UCRL-LR-105821-97-4, p.239
High Power Coherent Beam Combining Tech will be
demonstrated in ARC (Advanced Radiographic Capabilit)
laser.
N: Number of beams N times focus energy
N2 times peak intensity
Mode-Locking Laser and Phase-Locked Arrays
Mode-locking in the same volume generates ultrashort pulses.
Phase-locked array locks modes separated in space and frequency.
1
2
3
4
5
=const
Ultrashort pulses
Technique for translating light wave frequency by using an
optical ring circuit containing frequency shifter
Opt. Lett., vol. 17, 1307 - 1309, 1992.
K. Shimizu, T. Horiguchi, Y. Koyamada
G
AOM
+ 0+6
0+5 0+ 4
0+3 0+ 2
0+
-G
Problem: Max number of loop is limited by ASE amplification.
Basic concept of unlimited amplification: Zero gain amplification
Negative feedback for constant output
Spectrometer without dispersion elements
G
AOM
+ 0+6
0+5 0+ 4
0+3 0+ 2
0+
-G
0+6 0+5
0+ 4 0+3
0+ 2 0+
Broadband short pulse
Stabilized
pulse
Pulse compressor by AWG
+ fiber delay optics
MOPFA coherent array
•Complicated phase-locking servo system is required.
•Temperature drift & nonlinear phase fluctuation by huge B-integral
impose serious difficulty on scaling on power & array number
Straightforward, certain method..? N=2 10W S. Augst, T. Y. Fan et al., Opt. Lett. 29, 474 (2004).
N=4 2W J. Anderegg, M. Wickham et al., Photonics West 2003, 4974-03.
by courtesy of Dr. M. Wickham (Northrop Grumman)
High-power operation degrades phasing
H. Bruesselbach, M. Minden et al., CLEO 2005, CMDD4
HRL Lab.
“Longitudinal modes “collapse” and then constructive interference
supermodes cannot be maintained….”
“Self-organization by
nonlinear phasing”
9 of 19 can be phased.
Fiber laser coherent array by self-Fourier method By courtesy of Dr. C. J. Corcoran (Corcoran Engineering)
Appl. Phys. Lett. 86, 201118 (2005).
Linear Array with 7 Fiber Laser Elements
FL
Output
Fiber
Lasers
End
Mirror
Fourier
Lens
Microlens
Array
Cylindrical
Lens
Incoherent operation
(Mirror misaligned)
Coherent operation
(Mirror aligned)
Far-
Field
Far-
Field
Near-
Field
Near-
Field
predicted far field
F (F(x)) = F(x)
1W@1.07m7
Degree of
coherence = 0.73
WC1 2-Dimensional Waveguide Coherent Beam Combiner Scott Christensen and Olivia Koski
Lockheed Martin Coherent Technologies
Abstract: We report on a novel coherent beam combiner with the potential to completely eliminate
side-lobe power in the combined beam, without the use of vulnerable refractive or diffractive optical
elements in the beam train, allowing scaling to high power. We have completed a low power, 2-
dimensional proof-of-concept demonstration. The 2-D beam combiner can be used with various
lasers but is particularly well suited for combining the outputs of fiber lasers.
レーザー研究に関する共通問題 ELI, Gekko EXA 超高出力レーザーシステム 産業用高出力レーザー 重力波アンテナ PPM Loss Mirror 高エネルギー物理 コンプトン散乱 γ線発生 光子蓄積型光共振器 多モード光コム蓄積 ミラー損傷の研究は1980年代から進んでいない。 ミラー損傷のダイナミック観測研究 誘電体、固体表面内の光誘起電流の計測 Thin Disk Laser 接合技術の物理が必要 計測法の開発 マルチコアファイバーのコヒーレント位相同期技術
• Feed back mirror > Counter propagating beams > Standing wave > Density
modulation
• Standing density modulation locks the ignition position of the moving Bragg
grating.
• The Bragg grating locks the phase of the SBS wave.
• Phase controlling of SBS wave is possible by positioning the feed back mirror.
Concave MirrorLens
SBS Cell#1
SBS Cell #2
Concave Mirror
SBS Cell #1
SBS Cell #2
(a)Concentric type (b) Confocal type
“Self-phase control” method
Intensity profile of interference for 160 shots
Lens(f=250mm)
SBS Cell #1(l=500mm)
SBS Cell #2
Intensity profile of interference 0 50 100 150-180
-90
0
90
180
Ph
ase
diff
ere
nce
(d
eg
ree
)
Count of shots
Phase of the conventional SBS-PCM
H. J. Kong, S. K. Lee, and Y. S. Kim, “Phase locking of two beams using stimulated Brillouin phase conjugate
mirrors, LO2003, XIth Conference on Laser Optics, St. Petersburg, Russia (June 30 – July 04, 2003).
0 50 100 150 200-180
-90
0
90
180
Ph
ase
diffe
ren
ce
(d
eg
ree
)
Count of shots
Intensity profile of interference for 239 shots
Average fluctuation ~ λ/7.4
Confocal type
Phase controlled result – Wave-front division
H. J. Kong, S. K. Lee, and Y. S. Kim, “Phase locking of two beams using stimulated Brillouin phase conjugate
mirrors, LO2003, XIth Conference on Laser Optics, St. Petersburg, Russia (June 30 – July 04, 2003).
0 50 100 150 200-180
-90
0
90
180
(
deg
ree)
Count of shot
Ep=10 mJ
Intensity profile of interference for 220 shots
Average fluctuation ~ λ/35.7
Phase controlled result – Amplitude division
S. K. Lee, H. J. Kong, and M. Nakatsuka, Applied Physics Letters 87, 161109 (2005).
Experimental setup for the wave-front
dividing 4-beam combination
PB1&PBS2, polarizing beam splitters; HWP1&HWP2, half wave plate; P1, P2&P3, 45 degree prisms; BS, beam splitter; W,
wedged window; FR1, FR2, FR3&FR4, Faraday rotators; C1, C2, C3&C4, concave mirrors; PZT1, PZT2&PZT3,
piezoelectric translators.
FR1
Amplified
output
Input
beam SBS cell 1
SBS cell 2
Reference
beam
Nd:YAG laser
oscillatorHWP2
PBS1
PBS2
BSCCD
camera
P1
P2
P3
W
M1
M2
M3
AMP1
FR2AMP2
FR3AMP3
FR4AMP4
SBS cell 3
SBS cell 4
C1
C2
C3
C4
Phase control electronics
HWP1
6 mm
1.5 mm
4-beam aperture
f = -50 mm
f = 200 mm
f = -50 mm
f = 200 mm
Feedback
signal
PZT1
PZT2
PZT3
J. S. Shin, S. Park, H. J. Kong, and J. W. Yoon, Applied Physics Letters. 96.131116, 2010.
top related