Formation mechanism of high spatial frequency laser-induced periodic surface structures and experimental support

High spatial frequency laser-induced periodic surface structures (high-spatial frequency LIPSSs; HSFLs), being beyond the optical diffraction limit, have attracted great attention due to their outstanding physical characteristics and potential for use in various fields. However, the formation mechanism of HSFL is still controversial, which severely limits their further applications. In this work, a novel numerical model with experimental support are proposed to explain the formation of HSFL through the existence of subsurface plasmon polaritons (Sub-SPPs) generated at the subsurface of the material. According to the results, the period of HSFL is determined by the competition between the propagation loss of Sub-SPP and the penetration loss of fs-laser pulses. Given this competition, the HSFL formation can be investigated through the optical method by introducing a typical dielectric constant and thereby avoiding the discussion of complex electronic behavior. The numerical simulation results are in good agreement with the experimental data acquired on various materials, thus evidencing the applicability of this model. This work provides a clear physical picture of HSFL formation, allowing one to develop state-of-the-art surface morphology controlling methods for potential manufacturing applications.