Transition from isolated submicrometer pits to integral ablation of HfO2 and SiO2 films under subpicosecond irradiation

Damage behavior of HfO2 and SiO2 films under subpicosecond irradiation is investigated experimentally and theoretically in this work. The typical damage phenomenon is the transition from isolated submicrometer pits to integral ablation at transitive threshold. The experimental damage thresholds for both coatings are consistent with the theoretical calculation. The rate equation considering the feedback effect of electron number density is applied to calculate the deposited energy density, which illustrates the evolution of damage morphology.