A combined model for formation mechanism of ripples induced by femtosecond laser on silicon carbide

In this article, a comparative study is performed to explore the formation mechanism of laser-induced periodic surface structures (LIPSS) using femtosecond laser on silicon carbide (SiC). The optical properties of SiC transformed to a metal-like state when the excited carrier density exceeds 2e22 cm(-3) under laser irradiation and significantly altered the laser energy deposition. The laser-induced carrier density coupled with the optical properties and the incident laser intensity profile were calculated. The two-temperature model was used to describe the energy transformation from electron to lattice and guided to select appropriate laser conditions for producing ripples. The spatial period of laser-induced periodic nanostructures was calculated in frequency domain based on the Drude-Sipe model that comprised the estimation of free carrier density. The calculated range of the spatial period of LIPSS was about from 776 to 544 nm. Additionally, the experimental value was about 719-483 nm, which contained a good consistency with the theoretical results. This work provides a new approach for the prediction and fabrication of the LIPSS on SiC.