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GEO 600 Laser System as in the optics lab of Callinstraße 38 at 12.08.2000

LIGO-G000228-00-D. GEO 600 Laser System as in the optics lab of Callinstraße 38 at 12.08.2000. New Features of GEO 600 Slave Laser. Resonator spacer and base plate made of Invar (FeNi36 / 1.3912)

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GEO 600 Laser System as in the optics lab of Callinstraße 38 at 12.08.2000

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  1. LIGO-G000228-00-D GEO 600 Laser Systemas in the optics lab of Callinstraße 38 at 12.08.2000 ZA

  2. New Features of GEO 600 Slave Laser • Resonator spacer and base plate made of Invar (FeNi36 / 1.3912) • low thermal expansion   8x10-7 / K (average 20-50°C)(thermal change of optical path length in air at const. pressure   - 9x10-7 / K) • Diode laser power monitor ZA

  3. GEO 600 Slave Laser ZA

  4. GEO 600 Slave Laser ZA

  5. GEO 600 Slave Laser ZA

  6. “Long Term” Stability Maximum power after two mirrors and an adjustable attenuator consisting of a polarizer a half wave plate and a 2nd polarizer. Laser left untouched, attenuator varied for different purposes 2 % / 1.5 % pump power drop observed over full 21 day period ZA

  7. “Long Term” stability II(20 hpreliminary) All other acquired data stable to measurement resolution • room temperature: 1 K • pump power: 0.2 % • output power : 1% ZA

  8. Slave Intensity Noise Suppression ZA

  9. Slave Intensity Noise SuppressionTransfer ofPump Current Modulation to Amplitude Modulation ZA

  10. Slave Intensity Noise SuppressionFull Open Loop Transferfunction of AM Servo (preliminary setup) ZA

  11. Slave Intensity Noise SuppressionFirst Results (of preliminary setup) ZA

  12. Power Scaling of End Pumped Nd:YAG ZA

  13. Power Scaling of End Pumped Nd:YVO4 Advantages of Nd:YVO41) • amplifies 1064 nm emission of Nd:YAG(? at what temperature difference ?) • birerefingence na= 1.96 / nc= 2.17 no depolarization • emission || = 25x10-19 cm-2  = 7x10-19 cm-2 polarized emission • large product of || sp (sp  90 s) loss insensitive high gain lasers • 8 nm broad absorption @ 808 nm low requirements on pump diodes Disadvantage of Nd:YVO4 1) • low pump intensity damage threshold58 W / mm2 @ 0.5 % doping29 W / mm2 @ 1.0 % dopingincreased by 50 % by undoped endcaps 1) Data from Y.-F. Chen, IEEE J. Q. E. 35(2), 234 (1999) / Tsunekane et. al. Elt. Lett. 32(1), 41 (1996) / VLOC, Casix, Castech web pages ZA

  14. Problems of the slave • Atmospheric pressure changes • p dl/(l dp) 2.8x10-7 / hPa • 50 hPa and 0.5 m  7 m • Mirrors on single long range piezos tilt •  10 rad / m • Long range piezos have large low frequency resonances ZA

  15. Possible Solutions • Sophisticated piezo mountpre tension / damping / thick mirrorsmultiple piezos • Thermal length actuator30 mm Al/FeNi36  0.5 m/ Kpessimistic assumption: f 106 Hz / Hz1/2, fx-over 0.01 Hz piezo: lRMS 10 nm • Hermetically airproof resonatorconstant density of air  nearly constant optical path length expansion dependent on spacer material only Suprainvar / Zerodur / ULE ZA

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