Study of defects in fused silica via a Franck-Condon analysis

We present a spectroscopic study of defects in fused silica (SiO2) samples, showing their signatures in photoluminescence (PL) excitation and emission spectra, PL decay rate, and Fourier-transform infrared and Raman spectra. Using the multi-transition Franck-Condon (FC) analysis, we were able to characterize phonon coupling with oxygen-deficient centres (ODC) in fused silica. Four observed FC emission bands, located at 2.8, 3.2, 4.2, and 4.4 eV were identified as singlet-singlet and singlet-triplet transitions in two different types of ODC defect. This model was confirmed by PL decay data and allowed us to describe different emission pathways of ODC defects.