Surface and subsurface defects of optics are of major concern in improving laser induced damage threshold. SiO2single layers were fabricated by physical vapor deposition and sol-gel technique on fused silica substrates. HF acid etching and ultrasonic cleaning process are used to investigate the effect of surface and subsurface defects of substrates on the laser induced damage threshold (1-on-1, 8 ns at 355nm). Experimental data are then fitted with the Gaussian model of threshold distribution, which permits to discriminate different kinds of defects and extract their densities and threshold distribution. The interpretation of these data is further discussed according to their cleaning and fabrication method.
Subsurface defects of fused silica optics and laser induced damage at 351 nm
