Optical absorption, photoluminescence and electron paramagnetic resonance data were reported for non-irradiated and ultraviolet-irradiated Ge-doped silica. An analysis of the ultraviolet-induced effects showed that both components of the 5eV absorption band were partially bleached, as well as the photoluminescence which was excited within this absorption band. Also, more consistent ultraviolet-induced changes arose at higher energies, where bands at 5.8 and 6.4eV grew during treatment. Finally, Ge-E’ and Si-E’ electron paramagnetic resonance centers were generated; thus confirming their involvement in the photo-conversion process, but ruling out a previous attribution of the 6.4eV band to Ge-E’ centers. The absorption band at 6.4eV exhibited previously unobserved emission properties that were attributed due to excitation transfer processes.

B.Crivelli, M.Martini, F.Meinardi, A.Paleari, G.Spinolo: Physical Review B, 1996, 54[23], 16637-40