A high angular resolution interferometric backscatter meter

TL;DR

This paper presents a novel experimental method for directly measuring backscatter interference in interferometric systems, enabling precise quantification of backscatter from high-quality optics at very small angles.

Contribution

The paper introduces a new quantitative measurement technique for backscatter interference with high angular resolution, verified through experimental validation.

Findings

Able to measure backscatter at angles as low as 500 urad

Achieved an angular resolution of 160 urad

Validated the relation between backscatter, beam radius, and reflectance function

Abstract

Backscatter limits many interferometric measurements, including gravitational wave detectors, by creating spurious interference. We describe an experimental method to directly and quantitatively measure the backscatter interference. We derive and verify experimentally a relation between backscatter interference, beam radius and the scattering sample bidirectional reflectance distribution function. We also demonstrate that our method is able to measure backscatter from high quality optics for angles as low as 500 urad with a 160 urad angular resolution.