Examination of Possibility of Formation of Aggregated Color Centers in Inorganic Glasses and Their Application to Photochemical Hole Burning

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Aggregated F-centers such as M and R-centers show photochemical hole burning (PHB) in alkali halide crystals. If aggregated oxygen-deficient type point defects are produced in inorganic glasses, we may expect a possibility that PHB is realized in inorganic glasses without accompanying doping of a dye molecule as a PHB center. In this study, we examined the formation of aggregated color centers in inorganic glasses and of a pertinent hole in their optical absorption bands with a tunable laser light.The results obtained are summarized as follows :(1) Calcium aluminate glasses melted in strongly reduced atmosphere were found to show photochromism. Light-induced EPR led the conclusion that the photochromic center is an electron trapped at the site of oxygen vacancy surrouned by Ca^<2+> ions, i. e., likeF^+ center in CaO. No spectral hole formation was observed when the laser light illuminated the absorption band centered around 560 nm at 4.2K.(2) Two types of oxygen-deficient defects were produced in SiO_2 glass by implantation of Si^+orP^+, Si-Si bonds and neutral oxygen vacancies. Their concentrations are compatible to those of implanted ions, suggesting that implanted ions react chemically with oxygen in the substrate structure leaving oxygen deficiency defects. No zoro-phonon line was observed for either of these defects.