Power Stabilization to 3E-9 level
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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

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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

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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