Polariton Theory of Infrared Absorption Edges in SiO₂, GeO₂, and GeO₂‐Doped SiO₂ Glasses

Abstract

Abstract The infrared absorption edges of SiO 2 and GeO 2 glasses are calculated using a polariton theory. The glasses are modeled by sets of non‐interacting anharmonic oscillators with vibration frequencies equal to those of the asymmetric stretching motions of T–O–T (T  Si, Ge) bonds. The structural disorders of the glasses are considered by introducing distributions of the vibration freéuencies. The polariton effect as well as the contributions from other vibration modes in the glasses to the infrared absorption edges are studied. Furthermore, by a “mixed crystal” model, mixed up by three different oscillators corresponding to the asymmetric stretching motions of SiOSi, GeOGe, and SiOGe bonds, respectively, the infrared absorption edges in GeO 2 ‐doped SiO 2 glasses are calculated using the virtual crystal and superposition approximations to examine which one is closer to the experiments.