Photochemical reactions of Ge-related defects in 10GeO2·90SiO2 glass prepared by sol-gel process

Abstract

Germanosilicate glasses (10GeO2-90SiO2) were prepared by a sol-gel method and the ultraviolet-photosensitivity of glasses was investigated by optical absorption, electron spin resonance, and photoluminescence measurements. A one order larger intensity in the 5-eV absorption band was observed in the sol-gel glass sintered under an atmosphere at pressure <10-2 Torr, compared to a fiber preform of the same composition formed by a vapor phase axial deposition method. Changes in optical absorption were observed in the sol-gel derived glass by ultraviolet laser irradiation; a decrease in 5-eV band and increases in absorption around 4.5 and >5.7 eV were also noted. Photoluminescence intensity under 248-nm excitation decreased with an increase in laser fluence and with a corresponding decrease in the 5-eV band. This result implies that an ultraviolet-induced photochemical reaction from Ge2+ to Ge E′ in the glass had occurred.