Efficient generation of nearly arbitrary intensity profiles for optimizing high power laser machining processes

Adapting the intensity profiles of high power lasers provides a huge potential for the optimization of laser machining processes like welding, cutting or structuring in terms of quality and speed at the same time. However, as a result of thermal effects the intensity profiles and wavefronts emitted by multi-kilowatt lasers typically show a strong dependency on the output power. Besides these effects the conception and design of an appropriate beam shaping optics is further complicated due to the multimode properties of many high power lasers which results in unpredictable coherence properties. In this contribution we present the results of a comprehensive characterization of a beam, emitted by a high power disc laser including the temporal and power dependent behaviour of the intensity profile, the wavefront as well as coherence properties. Based on these results a design concept for generating nearly arbitrary intensity distributions in the processing plane with a high transfer efficiency and mostly independent from input beam variations is derived. Our approach is verified by a comparison of simulated and measured intensity profiles as well as beam shaping efficiencies.