Multishot laser damage of multilayer dielectric mirrors in the near-infrared subpicosecond regime

The laser damage resistance of dielectric components of high-power laser facilities to laser irradiation depends significantly on the irradiation sequence. In the short pulse (fs) regime, it is known that continuous irradiation of these components leads to a reduction in the damage threshold, reflecting a laser fatigue effect. Conversely, in the long pulse (ns) regime, progressive irradiation of these components leads to an increase in the damage threshold, reflecting a laser conditioning effect. In this article, we experimentally evaluate the competition between the effects of laser fatigue and laser conditioning for multilayer dielectric components irradiated in the subpicosecond pulse regime in the infrared (∼1µm) through different test sequences. For this purpose, we implemented an original test sequence derived from an S-on-1 type protocol, which consists of irradiating the component until damage. By repeating this sequence at different set points, it was possible to estimate the progressive reduction in damage threshold with the number of laser irradiations and to compare it with that observed during the fluence ramps. Particular attention was also paid to the precise knowledge of the test beam irradiating the component, as a dependence of the beam surface on the test set point was highlighted.