Electric field analysis coupled with the two-temperature model to elucidate the generation process of laser-induced periodic surface structure

A fundamental study of the mechanisms of generation of the laser-induced periodic surface structure (LIPSS) includes electromagnetic deposition theories and matter reorganization theories. The proposed two-dimensional finite element model incorporates frequency-domain electric field analysis and the two-temperature model (TTM) to simulate the growth process of LIPPS in multi-pulse picosecond laser irradiation. The proposed simulation proceeds as follows: the electric field intensity (EFI) distribution is calculated by referring to the material surface morphology and determines heat distribution by the electromagnetic heating (EMH); the heat distribution is introduced into the TTM to calculate the electron and lattice temperatures; by comparing the lattice and the vaporization temperature, material ablation is determined to obtain a new surface topography and single-pulse simulation completes; and by introducing the new surface topography recursively, multi-pulse laser irradiation can be simulated. In the calculation of a picosecond laser with a wavelength of 1064 nm, pulse duration of 20 ps and different laser fluences for the irradiation of the Ti6Al4V alloy surface, this method could simulate the ripple-like distributed EFI, and a surface morphology similar to that of LIPSS grew after several pulses. The results were in agreement with the observed experimental results. The proposed assumption is a novel approach for the explanation of the LIPSS generation mechanism.