High-fidelity recording periodic subwavelength 2D structures on silicon surface by femtosecond laser

The application of femtosecond laser-induced periodic surface structures (LIPSSs) is often hindered by unsatisfactory uniformity and homogeneous morphology. In this study, a high-fidelity recording technique is introduced for imprinting diverse two-dimensional (2D) LIPSSs on silicon surfaces via the two-step femtosecond laser exposure and chemical etching. This technique achieves the precise recording of gratings, serving as pre-LIPSSs, effectively avoiding the negative impacts of ablation debris and hydrodynamic instability. Furthermore, by repetitive laser exposure and polarization adjustment, the competition between localized field enhancement and overlapping effect enables the controllable imprinting of deepening gratings and various 2D LIPSSs. This technique significantly enhances the precision and flexibility of femtosecond laser micro/nano-processing.