LUMINESCENCE AND TRANSIENT ABSORPTION-BANDS IN FUSED SIO2 INDUCED BY KRF LASER-RADIATION AT VARIOUS TEMPERATURES

High purity fused silica with about 800 ppm OH content was irradiated with KrF laser radiation (248 nm) at temperatures between -180-degrees-C and room temperature. The laser-induced absorption at 215 nm (due to E' centers) was investigated. The generation rate of E' centers from a precursor state depends linearly on the applied energy density, indicating the presence of a one-photon generation process for E' centers in addition to the two-photon generation process from the silica network. The generation rate and relaxation of the 215 nm band is reduced at temperatures below room temperature. A luminescence band centered at 650 nm is excited during irradiation. A transient non-bridging oxygen center is postulated to explain the observed increase of the luminescence intensity with decreasing temperatures and with increasing radiation energy density.