Direct Observation of Broadband Coating Thermal Noise in a Suspended Interferometer

TL;DR

This paper reports the direct measurement of broadband thermal noise in high-reflectivity coatings used in gravitational-wave detectors, confirming previous indirect measurements and validating a key method for future detector development.

Contribution

It provides the first direct observation of coating thermal noise in a suspended interferometer, supporting the use of ring-down measurements for predicting thermal noise.

Findings

Direct observation matches predictions from ring-down measurements

Validates ring-down method for thermal noise estimation

Supports development of advanced gravitational-wave detectors

Abstract

We have directly observed broadband thermal noise in silica/tantala coatings in a high-sensitivity Fabry-Perot interferometer. Our result agrees well with the prediction based on indirect, ring-down measurements of coating mechanical loss, validating that method as a tool for the development of advanced interferometric gravitational-wave detectors.