Preferred concentration enhancement of photobleachable defects responsible for 5 eV optical absorption band in SiO2:GeO2 glass preform by heating in a H2 atmosphere

Abstract

Heat treatment of a 5GeO₂‐95SiO₂ glass preform in a H₂ atmosphere at 500 °C for 70 h increased intensities of an absorption band centered at 5 eV by a factor of ∼3. Intensities of photobleachable component, which is the precursor of UV‐induced Ge E’ centers and assigned to a neutral oxygen monovacancy, of the 5‐eV band were enhanced by a factor of ∼8 by heating. This increment is ∼3 times as large as that of UV‐unbleachable component, which is assigned to Ge²⁺ centers coordinated by two oxygens (neutral oxygen divacancy).