Optical materials for future gravitational wave detectors

Gravitational wave detectors are being blinded by their own mirrors, and this project aims to quiet them. The problem is thermal noise. At room temperature or cryogenic temperatures, the atoms in a detector’s mirrors and their coatings jitter slightly, creating a faint background rumble that masks the faintest gravitational wave signals. Current materials are not quiet enough. This project will measure the key optical properties—absorption, scattering, and mechanical loss—of novel mirror substrates and coatings, using specialised deposition facilities at the Centre for Extreme Performance Optical Coatings in Glasgow and a cryogenic prototype detector now under construction. If successful, the work will identify materials that produce less thermal noise, allowing future detectors to see deeper into the universe. This is fundamental science with no immediate practical application beyond astronomy. However, the optical coatings and precision measurement techniques developed here could eventually find uses in high-sensitivity sensors, laser systems, or quantum technologies—fields where controlling atomic-scale vibrations matters. For now, the goal is simply to make the quietest mirrors possible, so that the next generation of gravitational wave observatories can hear the universe more clearly.