Investigation of a Surface Layer Formed on Silica Glass as a Result of Mechanical-Chemical and Ionic Polishing

Optical parameters of a surface layer formed on silica glass in the process of polishing are studied. It is shown that the mechanisms of surface layer formation by mechanical-chemical and ionic polishing have much in common. In both cases, the appearance of a surface layer with a refractive index higher than that of the bulk glass is related to stretching and breaking of Si-O-Si bridging bonds due to hydrolysis during glass polishing. The hydrolysis of Si-O-Si bonds occurs with formation of Si-O and Si-OH groups, which leads to an increase in the refractive index of the surface layer.