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

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 the space gravitational wave detector of the LISA mission.

Space-based Gravitational Wave Observatories

“…Other noise sources associated with the interferometry include temperature dependent dispersion in the photo receivers and cables [44], timing jitter in the ADCs [126], scattered light [153,209], and optical pathlength changes on the optical benches and within the telescopes [198]. Most of these noise sources will likely be driven by temperature variations; LISA will likely require temperature fluctuations within each MOSA to be below 10 µK/ √ Hz and mK/ √ Hz for most of the other systems.…”

Coherent detection of the light backscattered by an optical surface

“…For all these GW interferometric instruments, parasitic light [10,11,12,13,14] is a critical noise source because, as a first order approximation, it can induce phase measurement errors depending on the relative amplitude of these parasitic optical fields. By way of example, this means that phase uncertainties of the order of a few microradians can be induced by ultra-weak retroreflected or back-scattered light, the relative power of which is about 10 −12 .…”