Present status of the laser system for KAGRA
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Present status of the laser system for KAGRA Univ. of Tokyo Mio Lab. Photon Science Center SUZUKI, Ken-ichiro
description
Present status of the laser system for KAGRA. Univ. of Tokyo Mio Lab. Photon Science Center SUZUKI, Ken-ichiro. Outline. Laser system Fiber laser amplifier Coherent addition Previous work Present status Summary & Future work. Laser System & Requirements. - PowerPoint PPT Presentation
Transcript of Present status of the laser system for KAGRA
Present status of the laser system for KAGRA
Univ. of Tokyo Mio Lab.
Photon Science Center
SUZUKI, Ken-ichiro
2014/06/20 6th KAGRA Workshop 2
Outline
• Laser system– Fiber laser amplifier– Coherent addition
• Previous work
• Present status
• Summary & Future work
2014/06/20 6th KAGRA Workshop 3
Laser System & Requirements
• MOPA (Fiber and Solid-state laser amplifiers) + Coherent Addition
Nd:YAG NPRO400mW
40W
80W180W
Fiber laser amplifiers
Solid-state laser amplifiers
Coherent addition on the beam splitter
40W
Requirements・ Laser power 180W・ Single frequency 1064nmSingle transverse mode TEM00
・ Linear polarization・ Low intensity noise・ Low frequency noise
Setup
• Widen dynamic range – Fiber stretchers• Same path length – good spatial mode matching
• Change water chiller
HWP HWPIsolator
15MHz
EOM
Nd:YAG NPRO400mW
Fiberstretcher
CollimatorFiber amplifier
Photo detector
MixerServo
Optical fiber system Free space optical system
Beam splitter
output
+ -
Previous work
78.9W was observed from two 40-W incident beams
2014/06/20 6th KAGRA Workshop 6
Optical System – fiber system
Fiber amplifiers
Seed laser (NPRO 400mW)
Fiber componentsIsolatorcouplerEOMstretcher
Power supply for NPRO
19 inch rack mounted
2014/06/20 6th KAGRA Workshop 7
Optical System – addition stageCollimators(Fiber amp. output) Isolators Beam splitter
Bright port
Dark port
Dark port optical system
2014/06/20 6th KAGRA Workshop 8
Experimental Result – long term operation
• Operation itself lasted 5 hours (Output power: 77 ～ 78W)
• The fiber stretchers had enough margin of control
• Large power fluctuation was observed for the first one hour
• Further brush-up is needed
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Pow
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Time[hour]
Bright portDark port
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Time[hour]
Stretcher1Stretcher2
Stable operation
output power of bright and dark port applied voltage of the fiber stretchers
Experiment Result – polarization fluctuation
• Power fluctuation results from polarization fluctuation
• Isolator is polarization dependent
• Polarization stability is important for power stability
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Pow
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Time[hour]
transmitted powercut off power
Collimator
HWP IsolatorTransmitted power
Cut off power
an example of power fluctuation
Experiment Result – fiber stretcher
2014/06/20 6th KAGRA Workshop 10
NPRO
Polarization rotation was seen at fiber stretcher.This may causes power fluctuation.
Fiber stretcher
Oscillo scope
PD
oscillator
Signal: 10Vp-p @100Hz
Setup
2014/06/20 6th KAGRA Workshop 11
Next Step – solid amplifier stage
• Use three Mitsubishi laser amplifiers
• Strong thermal lensing ( ～ 50cm/rod)
• Amplification of up to 180W is expected.
180W
Three solid-state laser amplifiers
80W
2014/06/20 6th KAGRA Workshop 12
Summary & Future work
• Coherent addition in new system was done
• Operation lasted 5 hours
• Longer operational term can be expected
• Control system worked well
• Noise evaluation of coherent addition
• Solid amplifier stage ( ～ 180W)
• Stabilization of intensity and frequency
