Third harmonic separator with high laser-induced damage threshold

Using electron beam evaporation, a 355 nm separator was designed by depositiing SiO2 and HfO2 alternatively. The coating has a reflectivity of larger than 99% at 355 nm through optimization and a transmittance larger than 99% at 532 nm and 1 064 nm. It has good electric-field distribution. The spectra of the fabricated coating is close to the designed one. The laser-induced damage threshold of the coating is 5.1 J/cm2. Morphology of laser-induced damage of the coating was characterized by differential interference contrast microscope．