# Apparatus to Measure Optical Scatter of Coatings Versus Annealing Temperature

## TL;DR

This paper introduces an imaging scatterometer designed to evaluate how crystal growth during annealing affects optical scatter in amorphous thin-film coatings, which is crucial for improving gravitational-wave detector sensitivity.

## Contribution

The paper presents a novel apparatus for measuring optical scatter of coatings as a function of annealing temperature, focusing on crystal growth effects.

## Key findings

- Crystal growth during annealing increases optical scatter.
- The apparatus effectively correlates annealing temperature with scatter levels.
- Potential for optimizing coating processes to reduce scatter.

## Abstract

Light scattered by amorphous thin-film optical coatings limits the sensitivity of interferometric gravitational-wave detectors. We describe an imaging scatterometer to assess the role that crystal growth during annealing plays in this scatter.