Radiative Thermal Noise for Transmissive Optics in Gravitational-Wave Detectors

TL;DR

This paper investigates the impact of radiative thermal noise in transmissive optics used in highly sensitive gravitational-wave detectors, deriving its magnitude and comparing it to other thermal noise sources.

Contribution

It introduces a new analysis of radiative thermal noise in transmissive optics, relevant for future gravitational-wave detector designs.

Findings

Radiative losses become significant in certain optical geometries.

Thermo-refractive noise from radiative losses is quantitatively derived.

Comparison shows radiative noise can dominate in specific regimes.

Abstract

Radiative losses have traditionally been neglected in the calculation of thermal noise of transmissive optical elements because for the most commonly used geometries they are small compared to losses due to thermal conduction. We explore the use of such transmissive optical elements in extremely noise-sensitive environments such as the arm cavities of future gravitational-wave interferometers. This drives us to a geometry regime where radiative losses are no longer negligible. In this paper we derive the thermo-refractive noise associated with such radiative losses and compare it to other known sources of thermal noise.