Corner reflectors and Quantum-Non-Demolition Measurements in gravitational wave antennae

TL;DR

This paper proposes using Fabry-Perot cavities with corner reflectors instead of spherical mirrors to reduce thermoelastic noise and improve sensitivity in gravitational wave detectors, demonstrating advantages in noise reduction and mode stability.

Contribution

It introduces a novel cavity design with corner reflectors that reduces thermo-refractive noise and mode distortion, enhancing gravitational wave detector performance.

Findings

Thermo-refractive noise in corner reflectors is substantially smaller than SQL.

Cavity mode distortion due to tilt/displacement is reduced with corner reflectors.

Corner reflectors exhibit less sensitivity to facet nonperpendicularity and material inhomogeneity.

Abstract

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) from 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 nonperpendicularity of corner facets and by optical inhomogeneity of fused silica which is proposed as a material for corner reflectors.