Single‐Pulse Nanomorphology Governs Laser‐Induced Periodic Surface Structure Formation on Metals

Abstract The targeted generation of laser‐induced periodic surface structures (LIPSS) is a powerful technique in modern surface engineering. While the dominant role of optical scattering and surface electromagnetic ways in LIPSS formation is widely acknowledged, formation mechanisms still pose open questions, particularly regarding material‐specific differences in uniformity and prominence. Here, a comparative pulse‐to‐pulse analysis of aluminum and stainless steel is presented, chosen to represent relevant metals that develop rough and smooth crater nanomorphologies, respectively, following single‐pulse irradiation. The findings reveal that the initial nanomorphology governs subsequent LIPSS development. After the initial pulse, aluminum forms pronounced spiky nanostructures characterized by elevated local surface gradients within the ablation crater, leading to strong scattering and localization of surface electromagnetic waves. This suppresses periodic intensity distribution and prevents the formation of LIPSS. In contrast, stainless steel retains a smooth crater morphology after the first pulse, enabling well‐defined systematic progression from high‐frequency to low‐frequency LIPSS. Supported by finite‐difference time‐domain simulations on measured surface topographies, the results quantitatively link initial nanomorphology to optical interactions, fundamentally defining material‐dependent pathways for LIPSS formation. Beyond previous explanations relying on macroscopic material parameters, this nanomorphological perspective provides an additional, yet direct explanation for inherent differences in LIPSS susceptibility among various metals.