How Can Amorphous Silicon Improve Current Gravitational-Wave Detectors?

Thermal noise in the highly reflective mirror coatings is one of the main limitations to the sensitivity of current gravitational-wave detectors. Amorphous silicon (aSi) is an ideal material to reduce thermal noise. Due to high optical absorption at 1064 nm, so far it was mainly considered as a candidate for future, cryogenic detectors using longer wavelengths. This paper summarizes the current state-of-the-art of the optical absorption of aSi at 1064 nm. We show how recent improvements in aSi absorption, and the development of multimaterial coatings, make the use of aSi at 1064 nm realistic, and discuss the possible thermal-noise improvement and corresponding optical absorption in room-temperature gravitational-wave detectors.