Towards finer 4H-SiC slicing: a spatiotemporally tailored combined pulse

Laser slicing of 4H-SiC can achieve low kerf loss and high efficiency, but it produces a rough surface degrading, processing quality. This Letter proposes a spatiotemporally tailored combined pulse (STT-CP) method, utilizing wavefront and temporal shaping of picosecond (ps) and nanosecond (ns) lasers based on the polarization state-dependent properties of the spatial light modulators, enabling aberration-free single ps laser focus with dual ns foci at different focal positions inside the material. This way, modification enhancement with a spatiotemporal interval is demonstrated, achieving 9 times larger internal modification width inside 4H-SiC than single ps pulse modification. Furthermore, a finer 4H-SiC wafer with a surface roughness of 93 nm and a slicing groove depth of 440 nm is sliced with dual ns laser foci separated by 5 μm at 100 ns time delay after the ps laser, highlighting the potential for finer material processing.