Hf1-xSixO2 Nanocomposite Coatings Prepared by Ion-Assisted Co-Evaporation Process for Low-Loss and High-LIDT Optics.

Jinlong Zhang,Xinbin Cheng,Zhanshan Wang,Xinshang Niu,Hongfei Jiao,Bin Ma

doi:10.3390/ma14102606

Abstract

Hf1−xSixO2 nanocomposites with different SiO2 doping ratios were synthesized using an ion-assisted co-evaporation process to achieve dense amorphous Hf1−xSixO2 coatings with low loss and a high laser-induced damage threshold (LIDT). The results showed that the Hf1−xSixO2 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 HfO2 grains were observed from 400 °C to 600 °C during annealing of the Hf0.80Si0.20O2 nanocomposites, resulting in excessive surface roughness. A phenomenological model was proposed to explain the phenomenon. The Hf1−xSixO2 nanocomposites (x = 0.3 and 0.4) maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm Hf0.70Si0.30O2/SiO2 high-performance reflector was prepared and achieved low optical loss (15.1 ppm) and a high LIDT (67 J/cm2).

Highlights

Optical coatings are enabling technologies for advanced laser systems, such as laser fusion facilities [1], gravitational wave detection systems [2], and ultra-short and ultraintense lasers [3]
We first describe the results of the refractive index and extinction coefficient analyses of the sets of Hf1−xSixO2 nanocomposites
The bond lengths of Hf-Hf and Hf-O are shorter for the Hf1−xSixO2 nanocomposites than the pure HfO2 film, resulting in a denser structure with smaller grains and a higher refractive index [20,30]

Summary

Introduction

Optical coatings are enabling technologies for advanced laser systems, such as laser fusion facilities [1], gravitational wave detection systems [2], and ultra-short and ultraintense lasers [3]. Their performance is highly dependent on the properties of the lowand high-index materials that constitute the multilayer coatings. It is desirable for the coating material to have a dense amorphous microstructure with low loss [4,5,6], a wide bandgap [7], and a high LIDT [8]. It is still quite challenging to obtain a dense and amorphous microstructure of HfO2 with extremely low absorption and scattering loss

Methods

Results

Conclusion