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The LIGO P re- S tabilized L aser

L aser I nterferometer G ravity Wave O bservatory. The LIGO P re- S tabilized L aser. Dr. Joseph Kovalik Scientist, LIGO Livingston. Overview. The LIGO Project Gravity Wave detection The LIGO interferometer Noise Sources Sensitivity Pre-Stabilized Laser

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The LIGO P re- S tabilized L aser

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  1. Laser Interferometer Gravity Wave Observatory The LIGOPre-Stabilized Laser Dr. Joseph Kovalik Scientist, LIGO Livingston

  2. Overview • The LIGO Project • Gravity Wave detection • The LIGO interferometer • Noise Sources • Sensitivity • Pre-Stabilized Laser • Master OscillatorPower Amplifier • Pre-Mode Cleaner • Frequency Stabilization Servo • Intensity Stabilization Servo The LIGO Pre-Stabilized Laser J. Kovalik

  3. . . Strength of Gravitational Waves change in length length • Tidal force with strain • Quadropole radiation • Amplitude Estimate • 1 km (103 m) baseline 10-18m centre of galaxy centre of cluster of galaxies The LIGO Pre-Stabilized Laser J. Kovalik

  4. Recycled Recombined Interferometer outer mirrors recycling cavity gain of 20 arm cavity gain of 100 recycling mirror inner mirrors The LIGO Pre-Stabilized Laser J. Kovalik

  5. Actual Optical Layout at Livingston The LIGO Pre-Stabilized Laser J. Kovalik

  6. The LIGO Sites LIGOHanford LIGOLivingston The LIGO Pre-Stabilized Laser J. Kovalik

  7. LIGO Livingston X arm Y arm The LIGO Pre-Stabilized Laser J. Kovalik

  8. Large Vacuum Equipment Area The LIGO Pre-Stabilized Laser J. Kovalik

  9. Noise Sources in an Interferometer • Seismic noise • due to ground vibration • filtered through a cascade of mechanical filters • mirror hung as pendulum • Newtonian noise (gravity gradient noise) • due to the local ground motion and atmospheric density fluctuations • ultimate limit to ground based interferometry • future: Laser Interferometric Space Antenna (LISA) • Shot noise • due to the counting statistics of the photons • reduced by increasing the laser power • resonant arm and recycling cavities • Radiation Pressure noise • due to the momentum of photons pushing on the mirrors The LIGO Pre-Stabilized Laser J. Kovalik

  10. Noise Sources (Continued) • Thermal Noise • kBT of energy in each (mechanical) degree of freedom of a system at thermodynamic equilibrium • manifests itself as a random fluctuation of the relevant observable • pendulum motion • internal modes of mirrors • use high Q materials to concentrate thermal noise at resonant frequency • And many more … • Residual gas fluctuations • Laser frequency noise • Laser amplitude noise • Creep Noise The LIGO Pre-Stabilized Laser J. Kovalik

  11. Predicted Noise Curves The LIGO Pre-Stabilized Laser J. Kovalik

  12. Preliminary Results • Science Run 1 • 3 interferometers in coincidence for 2 weeks in August 2002 • Science Run 2 • 3 interferometers in coincidence for 2 months February -March 2003 • Still commissioning The LIGO Pre-Stabilized Laser J. Kovalik

  13. Pre-stabilized Laser • 10 W laser at 1.06 mm • Solid State Nd:YAG Master Oscillator Power Amplifier • 700mW Non-Planar Ring Oscillator • double passed power amplifier • 4 Nd:YAG rods each pumped by a pair of 20 W laser diodes • Commercial product of Lightwave Electronics: 126 MOPA • Pre-Mode Cleaner • Create good TEM00 mode shape • Reduce intensity noise • Reduce output beam angular jitter • Frequency Stabilization • Ultimate interferometer linewidth of 1 Hz • Interferometer common mode rejection factor of 100 • Intensity Stabilization • Radiation pressure on mode cleaner optics causes frequency noise The LIGO Pre-Stabilized Laser J. Kovalik

  14. Thermal Enclosure Vacuum Pre-Stabilized Laser PSL Layout High Frequency Frequency Stabilization Amplifier RF Photodetector Fast Reference Cavity Slow Acousto-Optic Modulator Voltage Controlled Oscillator Wideband Input (from hanging mode cleaner) LSC Additive Input (from interferometer common arm length) Pockels Cell Power Stabilization Amplifier Mode Cleaner Transmission Photodetector Temperature Stabilization Amplifier PZT Current Adjust (slow) Current Shunt (fast) Tidal Input (from interferometer common arm length) LASER Power Amplifier Photodetector MOPA (Master Oscillator Power Amplifier) To Hanging Mode Cleaner Pre-Mode Cleaner Master Oscillator NPRO (Non-Planar Ring Oscillator) Pockels Cell Pockels Cell Pockels Cell Pockels Cell Power Adjust RF Photodetector Pre-Mode Cleaner Amplifier The LIGO Pre-Stabilized Laser J. Kovalik

  15. MOPA The LIGO Pre-Stabilized Laser J. Kovalik

  16. Pre-Stabilized Laser Table The LIGO Pre-Stabilized Laser J. Kovalik

  17. IF RF LO φ Pre-Mode Cleaner Servo Pre-Mode Cleaner Servo L1:PSL-PMC_ERR_F (16384) Mixer monitor DC Offset Mixer Monitor Blank Test 1 enable TEST 1 notch 70 kHz G=20 dB P=2 Hz Z=482 Hz Gain -10db to 30dB Mixer Offset Ramp TEST 2 Test 2 enable G=1 P=9.5 Hz HV amp G=50 twin t notch 15 kHz PZT PZT Voltage L1:PSL-PMC_PZT_F (2048) G=1/50 Pre-Mode Cleaner P=640 kHz Pre Mode Cleaner Cavity Pole Power Amplifier Camera PMC Transmission MOPA L1:PSL-PMC_RFPDC_F (256) L1:PSL-PMC_TRANSPD_F (256) RF Photodetector Pockels Cell PMC Reflection Master Oscillator NPRO To Interferometer RF 35.5 MHz The LIGO Pre-Stabilized Laser J. Kovalik

  18. Pre Mode Cleaner The LIGO Pre-Stabilized Laser J. Kovalik

  19. Pre-Mode Cleaner Servo Transfer Function The LIGO Pre-Stabilized Laser J. Kovalik

  20. Shot Noise Limit The LIGO Pre-Stabilized Laser J. Kovalik

  21. IF LO RF Thermal Enclosure Vacuum φ Frequency Stabilization Servo PCOut PC Monitor G=1/50 L1:PSL-FSS_MIXERM_F (16384) Mixer Monitor HV amp G=10 G=0 dB P=1Hz, 2 kHz, 3 kHz Z=DC, 100kHz Mixer monitor Fast Monitor TEST 2 L1:PSL-FSS_FAST_F (16384) Test 2 Enable Ramp TEST 1 Fast Out Ramp Enable Ramp Enable Test 1 Enable G=0 dB P=10Hz, 10 kHz, 20 kHz Digital PID Fast Gain -10db to 30dB Common Gain -10db to 30dB Mixer Offset Slow Actuator RF 21.5 MHz L1:PSL-FSS_SADRIVE_F (2048) RF 80 MHz Wideband Input (from hanging mode cleaner) RF Level L1:PSL-FSS_RFPDDC_F (256) Voltage Controlled Oscillator LSC Additive Input (from interferometer common arm length) Reflection Reference Cavity Internal wideband RF Photodetector Acousto Optic Modulator Power Amplifier Camera MOPA Pockels Cell Thermo-Electric Cooler Transmission P=35 kHz Reference Cavity Pole L1:PSL-FSS_RCTRANSPD_F (256) Pockels Cell P=640 kHz Pre Mode Cleaner Cavity Pole NPRO Pre-Mode Cleaner The LIGO Pre-Stabilized Laser J. Kovalik To Interferometer PZT

  22. Frequency Stabilization Servo Transfer Function The LIGO Pre-Stabilized Laser J. Kovalik

  23. Frequency Noise Spectrum The LIGO Pre-Stabilized Laser J. Kovalik

  24. Frequency Noise Spectrum (continued) The LIGO Pre-Stabilized Laser J. Kovalik

  25. Mirror Mounts New Focus Centre 840 Hz ??? New Focus Corner 840 Hz ??? Newport Ultima 100 (“open”) with 1” post -580 Hz Opto Sigma Ultra Stable 400 Hz Fixed Periscope 610 Hz Fixed “Sovietski” 1.4 kHz Ultima 100 with pyramid base 590 Hz Ultima AC (“closed”) with pyramid base 850Hz Micro Controle 730 Hz The LIGO Pre-Stabilized Laser J. Kovalik

  26. Frequency Jitter The LIGO Pre-Stabilized Laser J. Kovalik

  27. Intensity Stabilization Servo L1:PSL-ISS_INPDLOOP_F (16384) TEST IN Test Enable L1:PSL-ISS_EXC (16384) G=-10 P=52.9 Hz Z=DC To Interferometer TEST OUT 2 TEST OUT 1 IN PD MON In Loop Photodetector IN AC Level G=5 G=41 Loop Switch G=5 IN DC Level VGA Gain -10db to 30dB IN DC Offset OUT PD MON OUT DC Level OUT AC Level L1:PSL-ISS_OUTPDLOOP_F (16384) Mode Cleaner Out of Loop Photodetector G=-10 P=52.9 Hz Z=DC G=41 Out DC Offset MC3 L1:PSL-ISS_LFACTDRIVE_F (16384) MC 2 LF ACT DRIVE Current Adjust (slow) MC 1 Power Amplifier G=-4 P=101 Hz Z=2.1 kHz G=-4 P=101 Hz Z=2.1 kHz G=-10 P=1 Hz G=-4 P=796 kHz Z=4 kHz Current Shunt (fast) HF ACT DRIVE MOPA P=4 kHz Mode Cleaner Cavity Pole L1:PSL-ISS_HFACTDRIVE_F (16384) Master Oscillator NPRO The LIGO Pre-Stabilized Laser J. Kovalik

  28. Intensity Stabilization Servo Transfer Function The LIGO Pre-Stabilized Laser J. Kovalik

  29. Relative Intensity Noise The LIGO Pre-Stabilized Laser J. Kovalik

  30. Stabilized Intensity Noise The LIGO Pre-Stabilized Laser J. Kovalik

  31. Summary • LIGO interferometer needs a stable high power laser • The Laser Interferometer Gravity Wave Observatory is currently being commissioned • Begin continuous operation by 2004 • Copy of talk available at: http://www.ligo-la.caltech.edu/~kovalik/files/presentations/jpl_talk.pdf The LIGO Pre-Stabilized Laser J. Kovalik

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