1064Â nm nanosecond laser induced concentric rings and periodic ripples structures at the exit surface of fused silica

Commercial fused silica (50 mm diameter × 5 mm thickness) irradiated by single pulse of Nd:YAG laser (1064 nm, 12 ns) is experimentally investigated. The exit surface of fused silica is easier to be damaged than the entrance surface, so in this paper we only study the damage formed on the exit surface. The typical damage morphologies, irradiated at normal and oblique incidence, were observed with scanning electron microscope and atomic force microscope. The concentric ring structures with a central defect precursor are appeared in all damage sites. Furthermore, the whole damage sites are filled with the surface periodic striped structures, which direction is perpendicular to the incident electric field. Further analysis show that the incident energy has great effect on the size of damage sites, the depth of damage sites, and also the depth of the ripples, but has no effect on the period of the ripples. Additional experiments are performed to investigate the dependency between the period of ripples and the incident angle.