Measurement of Thermal Noise in Multilayer Coatings with Optimized Layer Thickness

TL;DR

This paper reports on direct measurements showing that optimizing layer thicknesses in multilayer optical coatings reduces thermal noise, which is crucial for enhancing the sensitivity of gravitational wave detectors.

Contribution

It presents the first direct measurement comparison between standard and optimized multilayer coatings, confirming modeling predictions of thermal noise reduction.

Findings

Optimized coatings exhibit lower thermal noise than standard designs.

Measurements align with theoretical modeling predictions.

Thermal noise reduction could improve gravitational wave detector sensitivity.

Abstract

A standard quarter-wavelength multilayer optical coating will produce the highest reflectivity for a given number of coating layers, but in general it will not yield the lowest thermal noise for a prescribed reflectivity. Coatings with the layer thicknesses optimized to minimize thermal noise could be useful in future generation interferometric gravitational wave detectors where coating thermal noise is expected to limit the sensitivity of the instrument. We present the results of direct measurements of the thermal noise of a standard quarter-wavelength coating and a low noise optimized coating. The measurements indicate a reduction in thermal noise in line with modeling predictions.