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Power Stabilization to 3E-9 Level: Optimizing Laser Systems for Enhanced Performance

Explore the latest advancements in power stabilization technology at the Max Planck Institute for Gravitational Physics, focusing on laser system optimization and minimizing external interference. Learn about critical factors, such as ground loop sensitivity, beam pointing control, and measurement techniques. Discover how to achieve power stabilization to the 3E-9 level for superior precision.

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Power Stabilization to 3E-9 Level: Optimizing Laser Systems for Enhanced Performance

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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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