Abstract
In recent years, real-time microscopic imaging of laser-induced periodic surface structure (LIPSS) formation during laser micromachining was found to be favorable for investigating the physical origin of the LIPSS on various materials. In this paper, an ultraviolet-oblique-illumination high-resolution microscopic imaging setup, combined with a focal spot enlarging technique, was used for observing the initiation, development, and maturation of the LIPSS. The research focuses on the influence of random surface deposits, laser-etched microtrench, and pre-existing ripples on laser-induced LIPSS under pulse-by-pulse irradiation. Compared to the flat region on the SiC surface, both random surface deposits and the microtrench promote the phase-locking growth of the LIPSS, but in different ways. The finite-difference time-domain method shows that random surface deposits may promote the LIPSS growth through the action of the interference field of incident light with its scattered light on deposits. A microtrench covered with high-spatial-frequency LIPSS may assist LIPSS growth by absorption enhancement-induced easier transferring of the incident periodic field. Finally, phase-locking growth of the LIPSS was found to be the result of the light-trapping effect of high-refractive-index sidewalls of the LIPSS valley. Our results showed that local morphologies were very important in LIPSS formation.
Funder
National Natural Science Foundation of China
Subject
Atomic and Molecular Physics, and Optics,Statistical and Nonlinear Physics