HfSiO Nanocomposite Coatings Prepared by Ion-Assisted Co-Evaporation Process for Low-Loss and High-LIDT Optics.

HfSiO nanocomposites with different SiO doping ratios were synthesized using an ion-assisted co-evaporation process to achieve dense amorphous HfSiO coatings with low loss and a high laser-induced damage threshold (LIDT). The results showed that the HfSiO nanocomposites (x ≥ 0.20) exhibited excellent comprehensive performance with a wide band gap and a dense amorphous microstructure. High-temperature annealing was carried out to ensure better stoichiometry and lower absorption. Precipitation and regrowth of HfO grains were observed from 400 °C to 600 °C during annealing of the HfSiO nanocomposites, resulting in excessive surface roughness. A phenomenological model was proposed to explain the phenomenon. The HfSiO nanocomposites (x = 0.3 and 0.4) maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm HfSiO/SiO high-performance reflector was prepared and achieved low optical loss (15.1 ppm) and a high LIDT (67 J/cm).