Femtosecond laser damage resistance of oxide and mixture oxide optical coatings

TLDR

The study investigates the laser damage resistance of ion beam‑sputtered oxide and oxide‑silica mixture coatings under 500‑fs, 1030‑nm pulses and proposes an empirical relation between refractive index and damage threshold. The authors measured LIDT, refractive index, and bandgaps of single‑layer coatings and analyzed how LIDT varies with refractive index to derive an empirical model. Pure oxides show a linear increase of LIDT with bandgap, matching photo‑ionization and avalanche‑ionization simulations, while oxide‑silica mixtures deviate from this trend.

Abstract

We report on the laser damage resistance of ion beam-sputtered oxide materials (Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2) and mixtures of Al2O3-SiO2, Nb2O5-SiO2, HfO2-SiO2, Ta2O5-SiO2, and ZrO2-SiO2, irradiated by single 500 fs pulses at 1030 nm. Laser-induced damage threshold (LIDT), refractive index, and bandgaps of the single-layer coatings are measured. For pure oxide materials a linear evolution of the LIDT with bandgap is observed. The results are in accordance with our simulations based on photo-ionization and avalanche-ionization. In the case of mixtures, however, deviations from the previous behaviors are evidenced. The evolution of the LIDT as a function of the refractive index is analyzed, and an empirical description of the relation between refractive index and LIDT is proposed.