Influences of Focusing Conditions on Dynamics of Laser Ablation at a Solid–Liquid Interface

Influences of focusing conditions relative to a sample surface on shock processes in under-liquid laser-induced ablation were studied using a custom-designed time-resolved photoelasticity imaging technique. A nanosecond laser pulse was focused onto the surface of epoxy-resin blocks immersed in liquids. When the surface was located close to the focal point, the breakdown that occurred on the solid–liquid interface resulted in reduced laser-induced stress. At positions above the focal point, the stress-wave intensity was mainly determined by laser pulse energy, but not by fluence. Impurities in liquids initiated breakdowns at multiple sites along the light path and reduced stress-wave intensity.