The optical loss study of molecular layer for a cryogenic interferometric gravitational-wave detector

TL;DR

This paper theoretically estimates the optical loss caused by molecular layers on cryogenic mirrors in gravitational-wave detectors, highlighting potential impacts on detector performance and emphasizing the importance of managing residual gas molecules.

Contribution

It provides a theoretical estimation of optical loss due to molecular layers on cryogenic mirrors, a factor previously not quantitatively analyzed for gravitational-wave detectors.

Findings

Residual gas molecules adhere to cryogenic mirror surfaces over time.

Molecular layers increase optical loss in the detector.

Optical loss impacts the sensitivity of cryogenic gravitational-wave detectors.

Abstract

The detection of gravitational-waves provides us with a deep insight into the universe. In order to increase the number of detectable gravitational-wave sources, several future gravitational-wave detectors will operate with cryogenic mirrors. Recent studies, however, showed residual gas molecules inside the vacuum chamber adhere to the cryogenic mirror surface and form a molecular layer which grows with time. The growing molecular layer introduces an additional optical loss in the mirror which can decrease the detector's performance. We theoretically estimate the optical loss by the molecular layer in a cryogenically operated gravitational-wave detector. The impacts on a cryogenic gravitational-wave detector is discussed based on the results of optical loss estimation.