Study of the coherent perturbation of a Michelson interferometer due to the return from a scattering surface

TL;DR

This paper presents a Michelson interferometry setup for precise measurement of backscattered light from optical surfaces, with applications in space gravitational wave detectors, achieving high sensitivity and analyzing scattering dependencies.

Contribution

It introduces a novel coherent measurement method for backscattered light and applies it to space detector conditions, including dust effects.

Findings

Achieved detection of backscattered light down to -130 dB.

Characterized backscattering dependence on spot position and angle.

Presented preliminary dust deposition scattering results.

Abstract

We describe a setup based on Michelson interferometry for coherent measurements of the backscattered light from a low roughness optical surface under test. Special data processing was developed for the extraction of the useful signal from the various stray contributions to the coherent signal. We achieve coherent detection of light scattered by a mirror down to -130 dB in optical power. We characterize the dependence of the backscattered light with spot position and incidence angle. Results of cross-polarization scattering coherent measurements and preliminary results of dust deposition experiment are presented here. This work represents the first step in the experimental evaluation of the coherent perturbation induced by the scattered light in space gravitational wave detector of the LISA mission.