Ultraviolet-photosensitive effect of sol-gel-derived GeO2-SiO2 glasses

Germanosilicate glasses are prepared by a sol-gel method and the ultraviole t (UV) photosensitivity of the glasses is investigated by optical absorptio n, electron spin resonance, and photoluminescence measurements. A KrF pulse d laser and a Hg lamp are used as UV light sources. The concentrations of i ntrinsic germanium-related oxygen-deficient centers in the glasses are succ essfully controlled by sintering conditions; in air or under reduced pressu re. One-order larger intensity of the 5 eV absorption band is observed in t he sol-gel glass sintered under the latter condition, as compared to a fibe r preform of almost the same composition, which is formed by the vapor-phas e axial deposition method. The effect of irradiation with KrF laser pulses on sol-gel glass is different from that on preform glass. On the other hand , the Hg-lamp illumination has the same effect on both sol-gel glass and pr eform glass. Based on these results, we discuss the defect states in sol-ge l-derived glass and fiber preform glass and also the mechanisms of photoche mical reactions under these two UV light sources. (C) 1999 American Institu te of Physics. [S0021-8979(99)06007-7].