Fundamentals of Scanning Surface Structuring by Ultrashort Laser Pulses: From Electron Diffusion to Final Morphology

Industrial use of ultrashort pulse surface structuring would significantly increase by effective utilization of the average laser powers available currently. However, the unexplained degradation of surfaces processed with numerous pulses at high average laser power makes this difficult. Based on a systematic experimental study, the structure formation underlying such surface degradation is investigated. Furthermore, a hierarchical structural formation model that bridges the gap between laser‐induced periodic surface structures and surface degradation is presented. Contrary to expectations based on previous research, less structure formation on titanium was observed for higher laser fluences. As a possible reason, enhanced electron diffusion with increasing intensity is investigated within the framework of the two‐temperature model. Our findings provide a deeper understanding of the microscopic mechanisms involved in surface structuring with ultrashort pulses.