Changes in the concentrations of the photo-induced paramagnetic centres, Ge E' centre, Ge electron centre and positively charged Ge lone-pair centre in four Ge-doped glasses with Ge contents of 1.0, 1.4, 6.9 or 9.2mol% were investigated by using a KrCl excimer lamp (5.6eV, 7.0mW/cm2) and a KrF excimer laser (5.0eV, 4MW/cm2) as photon sources. When the glasses were irradiated with photons from the lamp, the Ge E' centre and the Ge electron centre were induced in all of the glasses. The Ge lone-pair centre was observed only in samples with a Ge content of 1.4mol%, where the concentration of the induced Ge E' centre was smaller than that of the induced Ge electron centre. Laser photon-irradiation produced Ge electron centres and Ge lone-pair centres in all of the glasses. When laser photon irradiation was continued, Ge E' centres were introduced. The concentration of the Ge lone-pair centre was found to decrease with increasing concentration of the Ge E' centre. It was concluded that the generation of Ge E' centres decreased the concentration of Ge lone-pair centres.

Paramagnetic Centres Induced in Ge-Doped SiO2 Glass with UV Irradiation. M.Fujimaki, T.Katoh, T.Kasahara, N.Miyazaki, Y.Ohki: Journal of Physics - Condensed Matter, 1999, 11[12], 2589-94