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High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors

Grote, Hartmut, Weinert, Michael, Adhikari, Rana X., Affeldt, Christoph, Kringel, Volker, Leong, Jonathan, Lough, James, Lück, Harald, Schreiber, Emil, Strain, Kenneth A., Vahlbruch, Henning and Wittel, Holger 2016. High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors. Optics Express 24 (18) , 20107. 10.1364/OE.24.020107

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Current laser-interferometric gravitational wave detectors employ a self-homodyne readout scheme where a comparatively large light power (5–50 mW) is detected per photosensitive element. For best sensitivity to gravitational waves, signal levels as low as the quantum shot noise have to be measured as accurately as possible. The electronic noise of the detection circuit can produce a relevant limit to this accuracy, in particular when squeezed states of light are used to reduce the quantum noise. We present a new electronic circuit design reducing the electronic noise of the photodetection circuit in the audio band. In the application of this circuit at the gravitational-wave detector GEO 600 the shot-noise to electronic noise ratio was permanently improved by a factor of more than 4 above 1 kHz, while the dynamic range was improved by a factor of 7. The noise equivalent photocurrent of the implemented photodetector and circuit is about 5 µA/√ Hz above 1 kHz with a maximum detectable photocurrent of 20 mA. With the new circuit, the observed squeezing level in GEO 600 increased by 0.2 dB. The new circuit also creates headroom for higher laser power and more squeezing to be observed in the future in GEO 600 and is applicable to other optics experiments.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Publisher: Optical Society of America
ISSN: 1094-4087
Date of First Compliant Deposit: 5 February 2018
Date of Acceptance: 9 July 2016
Last Modified: 18 Jan 2021 23:34

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