Photochemical reactions which were induced by ultra-violet excimer laser irradiation were investigated (using electron spin resonance and optical absorption techniques) in 10mol%GeO2 glass fiber pre-forms and in SiO2 glass which had been implanted with Ge+ ions to a dose of 1016/cm2. Electron trapped centers which were associated with 4-fold coordinated Ge ions were formed in the fibers upon irradiation with 5eV KrF laser or 6.3eV ArF laser pulses. It was found that the concentration of 4-fold coordinated Ge ions increased as the square of the laser power. This implied that the formation reaction of such ions occurred via a 2-photon absorption process. It was noted that Si E’-centers (•SiO3, full-width at half-maximum = 3G) and peroxy radicals (Si-O-O- or O2-) formed in the glass which was implanted with Ge ions. These could be bleached by ultra-violet irradiation or by prolonged isochronal annealing. Exposure of the annealed glass to excimer laser pulses introduced Si E’ centers which had identical full-widths at half-maximum to those which were observed in the case of as-implanted glass. No ultraviolet-induced electron spin resonance signal which could be related to Ge ions was detected before or after annealing.

J.Nishii, A.Chayahara, K.Fukumi, K.Fujii, H.Yamanaka, H.Hosono, H.Kawazoe: Nuclear Instruments and Methods in Physics Research B, 1996, 116[1-4], 150-3