Control of the anisotropy in the formatin of silver precipitates in Ag-Cl containing glass

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During the course of the present research on the optically-induced anisotropy in the precipitates of glass, germanium-doped silica glass for optical fibers was found to be highly photosensitive against UV laser irradiation. Especially, the photosensitivity was significantily enhanced by a high-pressure hydrogen treatment. Thus, emphasis has been placed on the photosensitivity of germanuium-doped silica by means of the measurements of optical absorption in UV regions, photoluminescence (PL) , and electron spin resonance (ESR) .Polarized light with an energy of 36 eV from an undulator installed at BL 3A1 line of UVSOR was illuminated onto the germanium-doped silica glass. Photoluminescence and ESR measurements were carried out on the sample. In order to monitor photochemical reactions induced by light illumination, PL bands at 3.1 and 4.2 eV were measured. The decay of the PL follows a stretched exponential function, suggesting that the reaction occurs at the site of oxygen-deficient states in the germanium doped silica. The ESR of the germanium E'centers observed after the light illumination exhibit no angular dependence against the applied magnetic field.It is found that the formation of paramagnetic centers involves nonradiative relaxation of electron-hole pairs created by two-photon absorption of a KrF excimer laser. Refractive index changes induced by KrF laser illumination were investigated by the measurements of a Bragg reflection from a grating formed by illumination through a phase mask. The refractive index change was correlated with the formation of UV absorption bands. It is also found that high-dose gamma irradiation can produce clusters of Si in silica glass, which exhibit photoluminescene in the visible regions.