Evidence of refractive index change in glass substrates induced by high-density reactive ion plating deposition of SiO2 films

High-density reactive ion plating was used for SiO2 coating of Schott B270 glass. Optical properties of the sample were intensively studied by spectroscopic ellipsometry, reflectance and transmittance. Several optical models accounting for different structural defects, i.e., (1) gradient profile of refractive index in SiO2 layer, (2) transition layer between SiO2 and glass, and (3) induced slow variation of glass refractive index close to SiO2/glass interface were considered. The last one with increased value of substrate refractive index gave the best correspondence with the experimental data.