Adaptive Laser Modulation Strategy for Femtosecond Laser Surface Texturing of Uniform Microcorner Features

While laser surface texturing (LST) of adjacent segments with precipitous transition is a common phenomenon, how to realize uniform texturing quality particularly at the precipitous transition point is crucial for achieving the high performance of LST. Herein, the effectiveness of applying adaptive laser frequency modulation scheme in femtosecond LST of acute angles is demonstrated, where laser frequency is adjusted in real time according to laser spot movement speed to achieve a constant spot overlap ratio, despite texture geometry change. First, an experimental platform with synchronized control of galvanometer with laser source is established. Second, the morphological differences of ablated textures by the adaptive frequency modulation scheme and adaptive energy adjustment methods are characterized, and their underlying correlations with characteristics of laser spot movement are further revealed. Third, a linear energy density-based ablation depth prediction model is developed, and its universality under varying high spot overlap ratios is experimentally validated. Finally, the effectiveness of the adaptive frequency modulation in optimizing spatiotemporal coordination in laser–material interaction, as well as addressing abrupt quality degradation in transitional regions, is demonstrated, which accomplish the LST of highly consistent and controllable complex microtextures with acute angles on the laser-mechanical synchronization LST processing platform.