M. Weinert
Max Planck Society
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Publication
Featured researches published by M. Weinert.
Classical and Quantum Gravity | 2007
S. Hild; M. Brinkmann; Karsten Danzmann; H. Grote; M. Hewitson; J. Hough; H. Lück; I. W. Martin; K. Mossavi; N. Rainer; S. Reid; J. R. Smith; K. A. Strain; M. Weinert; P. A. Willems; B. Willke; W. Winkler
A widely used assumption within the gravitational-wave community has so far been that a test mass acts like a rigid body for frequencies in the detection band, i.e. for frequencies far below the first internal resonance. In this paper, we demonstrate that localized forces, applied for example by a photon pressure actuator, can result in a non-negligible elastic deformation of the test masses. For a photon pressure actuator setup used in the gravitational-wave detector GEO 600, we measured that this effect modifies the standard response function by 10% at 1 kHz and about 100% at 2.5 kHz.
Optics Express | 2016
Hartmut Grote; M. Weinert; R. Adhikari; C. Affeldt; V. Kringel; J. R. Leong; J. Lough; H. Lück; E. Schreiber; K. A. Strain; H. Vahlbruch; H. Wittel
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 5μA/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.
