Ultraviolet photon-induced absorption bands and paramagnetic centers in Ge and Sn co-doped SiO2 glass

Germanium and Sn co-doped SiO2 glass, a material for photosensitive optical fiber core that can be used for fabrication of optical fiber gratings, was exposed to photons from a KrF excimer laser (5.0 eV) or a XeCl lamp (4.0 eV). The photo-induced paramagnetic centers and optical properties of the glass have been examined with electron spin resonance and absorption measurements. Precursors of the paramagnetic centers are also discussed.