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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

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)

new power stabilization setup
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

dc ac coupled loop principle
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

power stabilization setup
Power Stabilization Setup

power stabilization to 3E-9 level - AEI Hannover

results dc ac coupled loop
Results – DC & AC Coupled Loop

Shot noise level 2E-9

power stabilization to 3E-9 level - AEI Hannover

critical factors
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

photodiode non uniformity pointing
Photodiode Non-uniformity & Pointing

spatial uniformity measurement

pointing measurement

(when) does it limit the performance ?

power stabilization to 3E-9 level - AEI Hannover

pointing sensitivity measurement
Pointing Sensitivity Measurement

EG&G C30642G

3 different methods  very good agreement

power stabilization to 3E-9 level - AEI Hannover

power fluctuations due to pointing
Power Fluctuations Due To Pointing

PMC: F=4100

power stabilization to 3E-9 level - AEI Hannover

low frequency noise in pd s
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

balanced detection setup
Balanced Detection Setup

power stabilization to 3E-9 level - AEI Hannover

balanced detection first experiment
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

balanced detection results 1
Balanced Detection – Results (1)

bias voltage dependence:

power stabilization to 3E-9 level - AEI Hannover

balanced detection results 2
Balanced Detection – Results (2)

temperature dependence:

power stabilization to 3E-9 level - AEI Hannover

balanced detection results 3
Balanced Detection – Results (3)

power dependence:

power stabilization to 3E-9 level - AEI Hannover

low frequency limit
Low Frequency Limit

:

PD low frequency noise limiting ?:

differentphotodiodes !!

power stabilization to 3E-9 level - AEI Hannover

conclusion next steps
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

spare slides
spare slides

power stabilization to 3E-9 level - AEI Hannover

photodiode temperature measurements
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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