Hf(1−x)Si(x)O(2) Nanocomposite Coatings Prepared by Ion-Assisted Co-Evaporation Process for Low-Loss and High-LIDT Optics

Hf(1)(−x)Si(x)O(2) nanocomposites with different SiO(2) doping ratios were synthesized using an ion-assisted co-evaporation process to achieve dense amorphous Hf(1)(−x)Si(x)O(2) coatings with low loss and a high laser-induced damage threshold (LIDT). The results showed that the Hf(1)(−x)Si(x)O(2) 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(2) grains were observed from 400 °C to 600 °C during annealing of the Hf(0.80)Si(0.20)O(2) nanocomposites, resulting in excessive surface roughness. A phenomenological model was proposed to explain the phenomenon. The Hf(1)(−x)Si(x)O(2) nanocomposites (x = 0.3 and 0.4) maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm Hf(0.70)Si(0.30)O(2)/SiO(2) high-performance reflector was prepared and achieved low optical loss (15.1 ppm) and a high LIDT (67 J/cm(2)).