Nanosecond laser induced damage mechanism of multilayer dielectric gratings

A multilayer dielectric grating used for laser pulse compression was designed. The gratings laser damage experiment was also performed. The observed damage morphologies cannot be interpreted only based on the usually used electromagnetic field distribution. Therefore, the temperature and thermal stress field distributions also have been calculated, and the affection of absorbing impurities and defects on the gratings damage process has been analyzed. The damage process happened in experiments is consistent with the theoretical predicted process, which is obtained based on the defects absorption. The absorptive defects are convinced to initialize the gratings damage. Defects located at different sites have different degrees of affection on the surface temperature and thermal stress distributions. Hence, the damage pits were appeared in different stages of laser irradiation and uneven distributed on the gratings surface.