Laser-irradiation-driven formation of oxygen-related defects and performance degradation in fused silica with nanosecond pulsed laser at 355 nm

摘要

Performance degradation and formation of oxygen-related defects in fused silica irradiated by large number of successive 355 nm laser pulses at low fluence were studied. Performance degradation was examined in view of optical transmission loss and decrease of laser-induced damage threshold (LIDT). When irradiated by 7200 shots at laser fluence of 4 J/cm(2), similar to 2% transmission loss and 25.4% decrease in LIDT were observed. What's more, LIDT data showed an exponentially decreasing trend with the increase of laser shots number. Laser-irradiation. driven oxygen-related defects were studied by combined methods of Fourier transform infrared radiometer, laser-excited Raman and X-ray photoelectron spectroscopies. Results suggested that laser irradiation induced formation of 3 fold (Si-O)(n )ring structure in pre-irradiated silica, and the content of 3 fold (Si-O)(n) rings increased with the laser shots. Laser-irradiation induced the formation and accumulation of low valence Si3+ and NBO ions as well as POL defects in silica. Formation and accumulation of POL defects and 3-fold (Si-O)(n) rings were suggested to be responsible for the observed significant performance degradation of fused silica.