Annealed and fine polished Ag and Cu samples are irradiated for 25, 50, 75, and 100 shots with a Q-Switched Nd:YAG laser in air and under high vacuum ~10−6 Torr. The irradiated samples are investigated under scanning electron microscopy, which reveals the formation of laser induced ripples structures with spacing 10 µm to 25 µm. Careful analysis revealed that the ripple spacing is not only dependent on laser wavelength, target properties, but also on the number of laser shots. It is also observed that ripples spacing varies from center to edge of the thermal damage zone. Two-fold spacing is measured near the edge compared to spacing at the center of the crater. Anisotropic stresses and stress waves (shock waves) are guiding the laser induced heat energy through particular channels. Splashing cones are developed with the increase in the laser shots. More theoretical investigations are needed to study the laser ripple periodicity in the context of laser shots effect.
