Investigation on the dynamic damage process of HfO2/SiO2 anti-reflection coatings under 1064nm nanosecond laser irradiation

Time-resolved pump-probe technology is an effective method to study the dynamic damage process of optics. In this paper, the dynamic damage process of HfO2/SiO2 anti-reflection coating, for the cases that the coating located on the laser incidence (forward process) and exit (reverse process) surface, irradiated by a 1064nm nanosecond laser was studied based on the time-resolved pump-probe technology of intensified charge-coupled device (ICCD). Under the irradiation of the same fluence (52J/cm2), pits without and with the layer peeling existed in both forward and reverse processes. However, the lateral size and depth of the small pits generated by the reverse process are larger than those of the forward process. The finite element analysis shows that the electric field intensity (EFI) on the substrate-coating interface for the forward and reverse processes is similar, which is not enough to form the difference in damage morphology. These results indicate the develop process of the plasma after its formation under the subsequent laser pulse irradiation determines the damage difference in the above two cases. The time-resolved study of anti-reflective coating damage is of great significance for its damage mechanism analysis and practical application.