Luminescence study of defects in silica glasses under near-UV excitation

Abstract : In this paper, we report the results of photo-luminescence experiments on high purity silica glass. Two different types of defects located on optical pieces are investigated: indented sites and laser damage craters. Visible luminescence excited at the wavelength of 325 nm (3.81 eV) is observed using confocal microscopy. Each type of defect produces qualitatively different luminescence spectra. In the case of indented sites, the well known Oxygen Deficient Center (ODC) band peaking at 2.75 eV is clearly observed, while for laser damage areas, another classical luminescent object is found: the Non Bridging Oxygen Hole Center (NBOHC) which peaks at 1.9 eV. On both types of defects, the luminescence spectra yield a strong peak around 2.2 eV but its interpretation is still controversory.