Corner reflectors and quantum-non-demolition measurements in gravitational wave antennae

We propose Fabry-Perot cavity with corner reflectors instead of spherical mirrors to reduce the contribution of thermoelastic noise in the coating which is relatively large for spherical mirrors and which prevents the sensitivity better than standard quantum limit (SQL) front being achieved in laser gravitational wave antenna. We demonstrate that thermo-refractive noise in corner reflector (CR) is substantially smaller than SQL. We show that the distortion of main mode of cavity with CR caused by tilt and displacement of one reflector is smaller than for cavity with spherical mirrors. We also consider the distortion caused by small non-perpendicularity of corner facets and by optical inhomogeneity of fused silica which is proposed as a material for corner reflectors. (C) 2004 Published by Elsevier B.V.