Photon pressure induced test mass deformation in gravitational-wave detectors

TL;DR

This paper shows that photon pressure can cause significant elastic deformation in gravitational-wave detector test masses, affecting their response function at kilohertz frequencies, which challenges the assumption of rigid body behavior.

Contribution

It demonstrates experimentally that photon pressure induces measurable elastic deformation in test masses, altering the response function in gravitational-wave detectors.

Findings

Deformation modifies response by 10% at 1 kHz

Deformation causes 100% change at 2.5 kHz

Photon pressure effects are significant at detection frequencies

Abstract

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.