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Laser system for LCGT. Norikatsu Mio* and Noriaki Ohmae* and the LCGT collaboration *Department of Advanced Materials Science, University of Tokyo. Outline. Power requirement for laser system of LCGT Design of the laser system Development of the prototype system Injection locked laser
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Laser system for LCGT Norikatsu Mio* and Noriaki Ohmae* and the LCGT collaboration *Department of Advanced Materials Science, University of Tokyo 58th Fujihara seminar
Outline • Power requirement for laser system of LCGT • Design of the laser system • Development of the prototype system • Injection locked laser • Stabilization system • Summary 58th Fujihara seminar
50 % Power requirement for laser system of LCGT 150 W 75 W 780 W Laser G=11 58th Fujihara seminar
Laser system of LCGT 58th Fujihara seminar
Design concept • Injection-locked laser: Clean and Stable optical mode • Power amplifier: Easy operation, possible expansion for higher power operation • Frequency control element • Intensity control element 58th Fujihara seminar
Injection locked laser • Master laser:2-W NPRO • Innolight Mephisto • Slave:100-W ring laser • Laser module:Mitsubishi • Resonator and Controller:U-Tokyo 58th Fujihara seminar
Laser module (Mitsubishi) Diffusive reflector +LD Two rods and rotator 58th Fujihara seminar
100-W Injection locked laser Innolight NPRO Mephisto 2000NE EOM 2W 2W FI FI lens 100W 85%,0.2mCX HR HR HR HR PD 100W HR,0.2mCX Piezoelectric transducer Quartz rotator Nd:YAG rod(Side-pumped) f=4mm, L=70mm Slave Laser • 100 W • Continuous wave(cw) • Single frequency • Dn ~ 1kHz • M2 ~ 1.1 • Linear polarization 58th Fujihara seminar
Output power of the slave laser • 121W by bidirectional oscillation M 2~1.1 58th Fujihara seminar
Realization of single frequency oscillation • Scanning Fabry-Perot output Free 100-W Single Frequency oscillation by injection locking Injection Locking 58th Fujihara seminar
Long term stability Continuous operation for more than 6 hours 58th Fujihara seminar
Frequency stabilization Pound-Drever-Hall technique To crystal temperature To piezoelectric transducer Mixer Reference cavity EOM Old EOM (RTA) Special EOM (Stoichiometric LiNbO3) 0.1W OSC 100W Wideband EOM (Stoichiometric LiNbO3) 100-W injection-locked Nd:YAG laser 58th Fujihara seminar
Bode plot of frequency control 330dB at 100Hz 170dB at 1kHz Piezo loop EOM loop “Wideband (UGF=100 kHz)” and “high-gain (170dB at 1 kHz)” control 58th Fujihara seminar
Opt-coupler Separate high current circuit and small control signal circuit Intensity stabilization using a current shunt • Current Shunt control 58th Fujihara seminar
Transfer function and noise suppression Transfer function of Amplifier Noise spectrum UFG=30 kHz 58th Fujihara seminar
Summary • Basic components for the LCGT laser have been completed. • 100-W single frequency operation has been achieved. • Wide range frequency and intensity control have been done. For a real interferometer, the laser must work for 24 hours a day, 365 days a year Further engineering work is necessary 58th Fujihara seminar
Thank you very much 58th Fujihara seminar
Frequency reference (P-polarization) • Ring resonator • Superinvar spacer • Tunable with PZT • FSR = 714MHz • Finesse~ 2900 (S) ~ 220 (P) • Linewidth(S) ~ 250 kHz • Transmission~ 80% 58th Fujihara seminar