Nanosecond multi-pulse damage investigation of optical coatings in atmosphere and vacuum environments

► We comparatively investigated the cumulative effect of multi-pulse irradiation of the dielectric mirror coatings in atmosphere and vacuum environments. ► For both environments, the laser-induced damage (LIDT) of the dielectric mirror coatings will decrease when shot number increase. ► The fatigue effect under repetitive shots in two environments will lead to different speeds of degradation. ► The formation of the sub-stoichiometry defect in the course of laser irradiation and air-vacuum effect is attributed to the different fatigue effect and degradation speed in two environments.