Ultrafast laser structuring within a process chain - influence of the surface morphology

Ultrafast laser processing has shown its advantages characterized by a highly precise ablation with minimal thermal influence in many applications. Many investigations deal with the laser inherent parameters like pulse duration, repetition frequency and scan speed to describe their influence on the machining quality. However, the final machining quality is also determined by the initial surface morphology. To combine the conflicting objectives of productivity and quality a multi-level photonic process chain is established. For this kind of process chain, the knowledge about the influence of the respective surface morphology on the subsequent process step is of importance. For that reason the development of the surface morphology is investigated for several ultrafast laser parameter settings and initial surface morphologies. In our investigations, we were able to establish a mathematical model that describes the development of the roughness as a function of the ablation depth.