Study of defects population and contaminations in silica/tantala coated mirrors

This article presents a study on the performance degradation of amorphous silica mirrors coated with silica/tantala, commonly utilized in gravitational wave interferometry measurements. The primary objective is to understand the factors contributing to the reduced performance, specifically the heightened noise observed after prolonged use of the mirrors in a vacuum. In this article, SiO2/Ta2O5 multilayered coated sample mirrors underwent analysis through x-ray photoemission spectro-microscopy, atomic force microscopy, and Raman spectroscopy, before and after exposure to a contaminating vacuum environment. Our findings revealed the possible correlation between the deterioration in mirror performance and an upsurge in contaminant carbon and defect populations within the silicon dioxide structure.