Intrafilm separation of solgel film under nanosecond irradiation.

We have observed large-scale intrafilm separation after the irradiation of solgel film with a single Nd:YAG pulse (1064 nm, 12 ns) in air. The irradiated but undamaged surface or the surface after intrafilm separation is densified. These damage features are distinctly different from the scalding surface of the electron beam evaporation coating or the ripple structures on the rear surface of fused silica, which indicates the extreme pressure gradients at the free surface-film interface. The submicrometer size melted cavity in the center of damage site is related with the nanoscale absorber. A phenomenological description that combines the defect-induced incubation phase and laser-supported surface breakdown wave is used to explain the damage process.