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).