Efficient fabrication of high-quality hybrid periodic nanostructures on 4H-SiC using a single-step vector femtosecond laser processing

Femtosecond lasers are widely recognized for generating laser-induced periodic surface structures (LIPSS) on various materials. Moreover, the homogeneous low spatial frequency LIPSS (H-LSFL) can be achieved by employing linear scanning with polarized femtosecond laser pulses and precise control of parameters, such as fluence and scanning speed. Unlike traditional LSFLs, these H-LSFLs are characterized by uniform structures. This study demonstrates the high-precision fabrication of hybrid periodic nanostructures, specifically H-LSFL with vertically aligned HSFL (high-spatial frequency LIPSS) on 4H-SiC using azimuthally polarized femtosecond laser beams. The experimental results revealed that the rapid fabrication of two parallel line patterns featuring hybrid periodic nanostructures can be achieved in a single scanning pass. Furthermore, a beam expander was employed to reduce the laser's focal spot size, increasing the distribution of HSFL concerning H-LSFL as the distance between line segments decreased.