Experimental study on the laser-matter-plume interaction and its effects on ablation characteristics during nanosecond pulsed laser scanning ablation process.

Abstract

Nanosecond pulsed lasers have been widely applied to interact with and characterize many different materials. For the purpose of a broader application, the current challenge is to achieve a speedup of ablation process, which is commonly thought to be possible by raising the on-target laser intensity. But the use of high intensity lasers results in severe laser-matter-plume interaction, leading to unwanted effects (e.g. saturation, shielding and thermal damage), which further affect the ablation process and ablation quality. However, laser-matter-plume interaction and its effects on ablation characteristics during laser scanning ablation processes are not well understood. In this paper, shadowgraph images and optical images during a laser ablation process were taken with a pump-probe shadowgraph imaging setup and an ultrahigh-speed camera. The results demonstrate that, under a high incoming laser density, laser-matter-plume interaction presents a periodical process, and thus cause a major impact on ablation regimes and microstructure formations. Moreover, the characteristics of micromorphologies and ejected particles suggest that the laser-matter-plume interaction has a significant influence on the ablation process, which, in turn, provides a more comprehensive understanding of the influence of laser-matter-plume interaction on the scanning ablation process. Consequently, laser-matter-plume interaction and its influence on the ablation process were summarized and clarified.