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.