Decay of ultraviolet-induced optical absorption in Ge-doped SiO₂ glass

We report quantitative measurements on the decay of optical absorption at various elevated temperatures in ultraviolet (UV)-irradiated SiO₂ glasses doped with Ge. From the Arrhenius plots of decay time constants, the activation energy of the GeE^′ center in the UV-irradiated glasses has been determined to be 2.4±0.3eV, while the reported activation energy of GeE^′ decay in UV-poled glasses is 0.4±0.1eV. The present experimental results strongly suggest that the decay process of the GeE^′ center induced in UV-irradiated glasses is quite different from that in UV-poled glasses.