Laser-induced damage of multilayer dielectric gratings with picosecond laser pulses under vacuum and air

•. Make first comparative laser damage experiments of MDG in vacuum and air.•The threshold follows a fitting scaling law of .•Contact angle of a liquid increases with glass pore size decrease.•Clean vacuum environment neither change the laser damage mechanism nor weaken LIDT of MDG.

In this study, laser damage tests of multilayer dielectric gratings (MDGs) are performed in vacuum (5×10−4 Pa) and in air at a wavelength of 1053 nm with pulse widths of 0.56 ps ~9.7 ps. The laser-induced damage threshold (LIDT) of MDGs in vacuum/air ranges from 2.1/2.2 J/cm2 to 4.4/4.8 J/cm2 for laser beams of normal incidence. The LIDT of MDGs follows a τ0.26 scaling in the pulse width regime considered. The typical damage morphologies in the two environments caused by the near threshold pulse were observed using a scanning electron microscope (SEM); the results indicate that the damage features of MDGs in vacuum are the same as those in air. The testing results reveal that a clean vacuum environment neither changes the laser damage mechanism nor lowers the LIDT of MDGs.