2.5D femtosecond laser microstructuring of complex surface patterns

Surface structuring aimed at improving aerodynamic, hydrodynamic, and wetting properties has gained traction as methods of material processing evolved and the need for highly efficient manufacturing manifested. Femtosecond laser processing has matured as a manufacturing method but remains limited in throughput and scalability due to the high precision required. Here we present a new concept for 2.5-dimensional surface structuring that simultaneously improves processing throughput and precision compared to traditional laser surface structuring approaches, leveraging the pulse-on-demand capabilities of the latest femtosecond laser sources. The approach is compatible with any repeatable and predictable scanning system, where we demonstrate an up to 10-fold increase in processing throughput compared to standard layer-by-layer material removal. Moreover, the precise pulse emission timing enables near-continuous variation in the laser pulse repetition rate, achieving pulse positioning precision equivalent to 30 ns timing steps. Further, we measure the material-dependent ablation response to changing laser pulse repetition rates, identifying intervals where the material removal rate is linearly scalable with the repetition rate while preserving the intrinsic high-quality of ultra-short laser processing. The proof of concept is a single-step femtosecond laser processing of surfaces based on a depth-encoded image input.