Current status ofLaser development

2nd Korea - Japan Workshop on KAGRA

2012/5/28(Mon)

Collaboration items

• High power amplifier• Pre-stabilization with fiber ring cavity

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Current status of the collaboration

• To start definite collaboration, we need some financial support.

• Prof. Yoon submitted his proposal concerning a high-power PCF fiber amplifier to Korean government.

• Mio submitted his proposal to Mitsubishi foundation with Prof. Yoon.

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We are waiting for good news!

Overview: Definition of Laser Subsystem• Laser subsystem consists of a laser oscillator, a power supply, a tiller,

control systems and monitor systems and an optical table.

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Laser output

Laser Oscillator

Power supply

Chiller

Monitor signals

Control signals

Circulating cooling water

DC/AC

Cooling water

3fAC200V1fAC200V

1fAC100V

3fAC200V

Input 　Optics

Clean room

bKagra: Target specifications

Item Value Wave length 1064 nm

Power 180 W

Oscillation mode Single (longitudinal and transversal)

Polarization Linear

Line-width < a few kHz

Frequency noise at 100 Hz

Frequency Control band-width

>800 kHz with an external EOM

Intensity noise (RIN) at 100 Hz

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Hz Hz/ 100

Hz/10 4

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Schematic diagram

Mitsubishi laser modules

Fiber laser amplifiers

NPRO(500mW)

40 W

40 W

80 W

200 W

The output of the NPRO is lead to two fiber amplifiers. Two outputs of the amplifiers are coherently added to obtain 80-W power. The laser light is introduced into three-stage solid-state amplifiers in order to obtain 180-W output power.

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Current Status for parts preparation

Mitsubishi laser modules

Fiber laser amplifiers

NPRO(500mW)

40 W

40 W

80 W

200 W

Power Supply Chiller

All components have been obtained and will be tested.

Delivery of the amplifiers is delayed because of a trouble on Faraday isolators that are set at the output fibers.

FR

FR

bKAGRA:Prototype test

• Performance of the fiber amplifier– 40-W one is being tested.

• Performance of the coherent addition system– The fringe contrast, phase stability and so on will be tested sonn.

• Performance of the laser module when used as an amplifier.– Optimization of the beam profile for obtaining the best amplification

performance.– Polarization stability, noise level should be tested; not started.

• Fix the specifications for the control system (interfaces to a PC and other systems)– Discussion about the assembling with a company is necessary .

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After the 1st Workshop

• No fiber amplifiers have not been delivered to us at the first workshop.

• One laser system was delivered to our lab in the middle of Feburuary.

• We have tested its phase noise using an interferometer.

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Intensity Noise

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1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E- 02 1.00E- 01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05

RIN

[1/r

Hz]

周波数 [Hz]

アンプ前後のRIN比較

NPRO

40WAmp後

30WAmp後

20WAMP後

10WAmp後

Relative Intensity Noise

Frequency (Hz)102 104100

10− 3

10− 5

10− 1

10− 7

10-W Amplifier

Phase Noise Measurement

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Measurement System

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Amplified laser light

Seed laser light PZT Mirror

Control Circuit

Phase Noise

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Phase Noise

10− 3

10− 5

10− 1

Frequency (Hz)103 104102

New lab@Hongo

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We moved our lab from Kashiwa to Hongo in March. Most of our experimental systems are still in boxes.

Laser Development @ Hongo• Phase noise

measurement has been started.

• We decided not to use a fiber-coupled Faraday isolator.

• Two lasers will be available in June; a coherent addition system can be tested soon.

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Summary

• The performance of the 40-W fiber amplifier is not so good as 10-W one; we need further investigation.

• Choice of fiber coupled optical devices for high power laser should be careful ; the heat due to the light loss is quite serious.

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