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.