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Power Stabilization to 3E-9 level

Power Stabilization to 3E-9 level. Frank Seifert, Patrick Kwee, Michele Heurs Benno Willke, Karsten Danzmann Max-Planck-Institute for Gravitational Physics (Albert-Einstein-Institute) University of Hannover LSC Hanford, March 21th, 2006 LIGO-G060115-00-Z.

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Power Stabilization to 3E-9 level

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  1. Power Stabilization to 3E-9 level Frank Seifert, Patrick Kwee, Michele Heurs Benno Willke, Karsten Danzmann Max-Planck-Institute for Gravitational Physics(Albert-Einstein-Institute) University of Hannover LSC Hanford, March 21th, 2006 LIGO-G060115-00-Z Max Planck Institute for Gravitational Physics (Albert Einstein Institute)

  2. New Power Stabilization Setup • laser system:- as simple as possible- prevent x-coupling of laser diode current into other observables (frequency, beam geometry, etc.)  NPRO &power actuator independent from laser system (e.g. AOM) • beam pointing:- may limit at 10-9-level at low frequencies- filtering or active stabilization required ?- use of different photodiodes? (larger ?) filtering by PMC (F≈4100) & whole setup in vacuum & same photodiodes as before • photodiode temperature:- chip temperature increases ≈ 10K (P=130mW)- temperature coefficient ≈ 0.039 %/K (Datasheet Perkin Elmer) active temperature stabilization • optimization of stabilization loop- DC-coupled loop for stable operating point- AC-coupled loop for lowest noise DC & AC-coupled loop power stabilization to 3E-9 level - AEI Hannover

  3. DC & AC-coupled loop - Principle Advantage: - DC-coupled loop for stable operating point- AC-coupled loop for lowest noise (not limited by noise of voltage reference) power stabilization to 3E-9 level - AEI Hannover

  4. Power Stabilization Setup power stabilization to 3E-9 level - AEI Hannover

  5. Results – DC & AC Coupled Loop Shot noise level 2E-9 power stabilization to 3E-9 level - AEI Hannover

  6. Critical Factors • very (!) sensitive to ground loops avoid any (!) ground loop, even at RF (capacitive coupling) independent supply of components battery powered devices • beam pointing  reduction by PMC (passive filtering) proper adjustment of photodiodes (minimize with impressed pointing) (PZT behind PMC) • acoustics  shielded environment proper mechanical design • air currentsvacuum power stabilization to 3E-9 level - AEI Hannover

  7. Photodiode Non-uniformity & Pointing spatial uniformity measurement pointing measurement (when) does it limit the performance ? power stabilization to 3E-9 level - AEI Hannover

  8. Pointing Sensitivity Measurement EG&G C30642G 3 different methods  very good agreement power stabilization to 3E-9 level - AEI Hannover

  9. Power Fluctuations Due To Pointing PMC: F=4100 power stabilization to 3E-9 level - AEI Hannover

  10. Low Frequency Noise in PD‘s Balanced detection setup • pre-stabilized laser system below 1E-8 level • amplification aftersubstraction of photocurrents • temperature stabilized photodiodes • vacuum tank power stabilization to 3E-9 level - AEI Hannover

  11. Balanced Detection Setup power stabilization to 3E-9 level - AEI Hannover

  12. Balanced Detection – First Experiment unknown noise source nearly shot noise limited first test of balanced detection setup with large area Si photodiodeswithout temperature stabilization: power stabilization to 3E-9 level - AEI Hannover

  13. Balanced Detection – Results (1) bias voltage dependence: power stabilization to 3E-9 level - AEI Hannover

  14. Balanced Detection – Results (2) temperature dependence: power stabilization to 3E-9 level - AEI Hannover

  15. Balanced Detection – Results (3) power dependence: power stabilization to 3E-9 level - AEI Hannover

  16. Low Frequency Limit : PD low frequency noise limiting ?: differentphotodiodes !! power stabilization to 3E-9 level - AEI Hannover

  17. Conclusion & Next Steps • Still limited by unidentified noise source at low frequencies low frequency noise in PD‘s good candidate • future experiments: • low frequency noise in photodiodes detailed characterization of different photodiodes (dependence on bias voltage, temperature, photocurrent, manufacturer, material (InGaAs, Ge), size (2mm, 3mm)) • influence of temperature fluctuations at the beamsplitter temperature coefficient of the BS  TF temperature to RIN • influence of photodiode temperature fluctutionstemperature coefficient of PD‘s TF temperature to RIN power stabilization to 3E-9 level - AEI Hannover

  18. spare slides power stabilization to 3E-9 level - AEI Hannover

  19. Photodiode Temperature Measurements P = 65 mW P = 105 mW P = 130 mW • ∆T only ≈ 10K • real chip temperature ? P = 0 mW PD EG&G C30642G without window power stabilization to 3E-9 level - AEI Hannover

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