Femtosecond laser two-beam interference applied to 4H-SiC surface hierarchical micro-nano structure fabrication

This study used the ultrashort pulsed direct laser interference patterning (USP-DLIP) and a single Gaussian beam process to generate the surface structures on 4H-SiC. The diffractive optical element separated the single beam into two beams and then interfered on the 4H-SiC surface for material processing. The experimental results obtained by USP-DLIP and a single Gaussian beam process were compared. USP-DLIP uses the superposition of two femtosecond laser beams to re-adjust the laser energy distribution. It is characterized by simultaneously producing hierarchical surface structures, e.g., DLIP structure, high spatial frequency LIPSS (HSFL), and low spatial frequency LIPSS (LSFL). Also, the aspect ratio control capability of USP-DLIP is higher than that of a single Gaussian beam. Furthermore, after 4H-SiC was irradiated with USP-DLIP, the Raman results found that the peak of crystalline SiC decreased more than single-beam irradiation.