Laser-induced bulk damage of UBK7 glass owing to its rear-surface defects
Pulsed laser induced bulk damage of UBK7 glass at 1064nm was studied. Damage morphologies of UBK7 were observed with a microscope. Laser induced damage thresholds(LIDT) of the glass's surface and bulk were tested using automated damage test facility. Thread damage between rear surface and bulk burst was detected from the damage morphologies. The conclusion that defects and impurities on the rear surface caused bulk damage was drawn. When the defects on rear surface absorb incident light, plasma was produced and it spread to the front rapidly. Then the high temperature and high pressure of the plasma caused surface and bulk damage of the material. The details of surface and bulk damage mechanism were also analyzed. The LIDT of rear surface is lower than that of front surface because of the light intensity modulations caused by opaque obstacles on the front. The decrease of defects on surface can not only increase surface damage threshold but also improve bulk damage threshold.