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 article 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 GEO600 we measured that this effect modifies the standard response function by 10% at 1 kHz and about 100% at 2.5 kHz.
@article{arxiv.0710.1229,
title = {Photon pressure induced test mass deformation in gravitational-wave detectors},
author = {S. Hild and M. Brinkmann and K. Danzmann and H. Grote and M. Hewitson and J. Hough and H. Lueck and I. Martin and K. Mossavi and N. Rainer and S. Reid and J. R. Smith and K. Strain and M. Weinert and P. Willems and B. Willke and W. Winkler},
journal= {arXiv preprint arXiv:0710.1229},
year = {2008}
}