Picosecond laser-induced damage of HfO2-Al2O3 mixture-based mirror coatings in atmosphere and vacuum environments

The performance of a mixture-based picosecond laser mirror (MPLM) coating, particularly the picosecond (ps) laser-induced damage threshold (LIDT), is investigated. Two types of 1053 nm ps laser mirror coatings are deposited using electron-beam evaporation: an MPLM coating consists of alternating layers of the HfO2-Al2O3 mixture and SiO2, and a traditional picosecond laser mirror (TPLM) coating consists of alternating layers of HfO2 and SiO2. Comparative studies on the optical, microstructural and mechanical properties, and LIDT are carried out. For an s-polarized 8 ps laser pulse at a wavelength of 1053 nm, the ps-LIDT of the MPLM coating is approximately 1.2 times higher than that of the TPLM coating in both atmosphere and vacuum test environments. Typical damage morphologies and laser-induced temperature simulations by finite element modeling suggest that the enhanced LIDT of the MPLM coating may be attributed to the lower laser-induced temperature rise in the MPLM coating.