Laser-induced damage of transmissive optics at 1064 nm

In this paper, the laser damage of transmissive optics used in high power Nd:YAG laser was studied in details by use of Nd:YAG damage testing system, the damage experiment was taken by 1-on-1 damage measurement method, and the damage morphology was observed by 200X Normaski microscope. The wavelength of laser is 1064nm and the duration of pulse is 10ns. Experiment result shows that the damage morphology of transmissive optics such as AR coatings and polarizer has same damage shape-pinhole, which is notable different from that of HR coatings. The pinhole is about round with diameter 10-50um, separated on the damage area of coatings and deep to the surface and sub-surface of the substrate. Specially, the damage pinhole exhibits on the rear surface of AR coatings and on the front surface of the polarizer respectively. On certain range of the laser energy density, the density improvement don't increase the size of the pinhole, just only increases the amounts of the pinhole. We think the pinhole is mainly induced by standing wave electrical field formed by laser and the defects near the both surface of the substrate.