Laser system for LCGT

Norikatsu MIO

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Power requirement for LGCT laser 150 W Laser 50 % 75 W 780 W G=11 2

Laser system for LCGT • 150W Output ： MOPA Injection locking + 3

Design concept • Injection-locked laser: Stable optical mode Frequency control element • Power amplifier: Easy operation, Cascadable for higher power operation Intensity control element 4

Injection locked laser • Maser laser ：２ -W NPRO – Innolight Mephisto • Slave ： 100-W ring laser – Laser module ： Mitsubishi – Resonator and Controller ： U-Tokyo 5

Laser module （ Mitsubishi ） Two rods and rotator Diffusive reflector +LD 6

Slave laser • Ring laser with two laser modules 7

Output power of the slave laser • １２１ W by bidirectional oscillation 8

100-W Power laser • Injection locking with 2-W master laser (NPRO) 9

Realization of single frequency oscillation • Scanning Fabry-Perot output Free Injection Locking 100-W Single Frequency oscillation by injection locking 10

Long term stability Continuous operation for more than 6 hours 11

MOPA and intensity stabilization (test bench)

Master NPRO FR Amplifier

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Intensity stabilization performance Unity Gain freq.

30kHz Loop Gain at 100 Hz 100db 13

Ongoing experiments • Frequency stabilization of the 100-W laser.

• EOM test for high-power laser light.

– MgO-doped Stoichiometric LiNbO 3 • Final stage amplifier (50W) will be tested soon.

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Frequency stabilization experiment • Triangular reference cavity ( Dn=152 kHz) • Transmission intensity curve Feedback system is being developed 15

Summary • Basic components for the LCGT laser have been completed.

– 100-W single frequency operation has been achieved.

– Wide range intensity control has been done by the current-shunt method.

• Further experiments for frequency and intensity control are being performed.

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