Photoluminescence from defect centers in high-purity silica glasses observed under 7.9-eV excitation

Photoluminescence under 7.9-eV excimer-laser excitation was measured at room temperature on various types of high-purity silica glasses, which were classified based on the oxygen stoichiometry and OH concentrations. Several luminescence bands with different peak energies from 1.9 to 4.3 eV and decay constants were observed in different types of silicas. The 1.9-eV band was observed in low-OH oxygen-surplus and high-OH silicas. The 2.7-eV band was observed only in low-OH oxygen-deficient silicas. The 3.1- and the 4.2-eV bands were observed in a particular type of silica, which has a characteristic absorption band at 5.1 eV (referred to as the B2 band). The 4.3-eV band was observed in all types of silicas but the oxygen-surplus type. These results indicate that defects responsible for these luminescence bands are diamagnetic defects introduced during preparation or paramagnetic species induced during excitation.