Photochemical reactions of Ge-related defects in 10GeO(2) center dot 90SiO(2) glass prepared by sol-gel process

Germanosilicate glasses (10GeO(2)-90SiO(2)) were prepared by a sol-gel meth od and the ultraviolet-photosensitivity of glasses was investigated by opti cal 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, co mpared to a fiber preform of the same composition formed by a vapor phase a xial 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. Ph otoluminescence intensity under 248-nm excitation decreased with an increas e 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 EE in the glass had occurred. (C) 1999 Elsevier Science B.V. All ri ghts reserved.