Alumina as Mirror Coating Material For Gravitational Wave Detectors

Ten years after the Laser Interferometer Gravitational-Wave Observatory (LIGO) achieved the first detection of gravitational waves, the field of gravitational-wave astronomy is flourishing, with approximately 300 detections to date. Further improvements in detector sensitivity—and the development of next-generation instruments—depend on advances across several technological areas, including the creation of mirror coatings with reduced thermal noise and optical absorption.

The current LIGO optics employ ion-beam–deposited amorphous oxide coatings. Amorphous oxides, such as amorphous alumina (Al₂O₃), are also among the leading candidate materials to make improved-performance coatings. In this talk, I will present computational results examining how deposition conditions—particularly substrate temperature—affect the atomic structure of amorphous alumina. I will also discuss whether these simulations indicate the feasibility of achieving ultra–low–mechanical-loss coatings through deposition at elevated substrate temperatures.