Laser-induced damage behaviors of antireflective coatings at cryogenic condition

The laser-induced damage to antireflective coatings on Yb:YAG crystals under different temperatures was investigated. An optical profiler, field-emission scanning-electron microscopy, and a step profiler were used to determine the damage morphology, including size and depth. The results show that there is about 5 J/cm(2) decrease in the laser-induced damage threshold of cryogenic conditions compared to that of room temperature in 1-on-1 test mode, and a 3 J/cm(2) decrease in 100-on-1 mode. There is an accumulation effect in both cases. Meanwhile, the damage areas and depths are also much larger under cryogenic conditions. The precipitation of the subsurface defects in the substrate and the thermal stress in the interface between the film and the substrate under cryogenic conditions are considered to be the key factors in the unique damage behaviors.