Effect of laser-induced zinc micro-spheres on enhanced absorption of subsequent pulse laser

Abstract

Numerous football-shaped Zinc micro-spheres on inner surface of the crater are produced by pulsed laser ablation of Zn metals in vacuum condition (～2 Pa). Pulsed laser induced plasma emission spectrum is measured to reveal the effects of macro- and micro-structures on subsequent pulse laser ablation. The intensity of spectral line at 334.5 nm originating from Zn atoms by subsequent laser ablation of the ablated spot is 10.3% higher than that created over a smooth surface. The intensity of the same spectral line produced over a ablated spot with a great number of micro-spheres is 1.343 times higher than that produced by the plasma generated over the ablated spot. The Zn micro-sphere completely covered with nano-scaled regular pentagonal and hexagonal facets can lead to an enhanced absorption of the following laser energy. The total number of Zn micro-spheres increases as the number of laser shots increses, which can result in hotter and dense plasma by subsequent laser ablation. The proposed results are of importance for developing the laser micro-drilling technique.