Metal dielectric gratings with high femtosecond laser damage threshold of twice as much as that of traditional gold gratings

We report on the development of metal dielectric gratings (MDG) including two layers of gold film and a silica layer, which is simple and has enough broadband with 105 nm over 90%. The measured laser-induced damage threshold (LIDT) on the grating surface is 0.40 J/cm(2) at a pulse duration of 32 fs, which is twice more than that of gold gratings, and the initial damage comes from nodule defects. Laser-induced ionization theory is first used to study the effect of nodule defects on LIDT of MDG and predict the maximum LIDT of the perfect MDG. The prediction value of the MDG without nodule defects is 0.60 J/cm(2) on the grating surface, which has tremendous application potential in petawatt-class laser systems. (C) 2019 Optical Society of America