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High Power Laser Processing with Ultrafast and Multi-Parallel Beams

: Gillner, A.; Finger, J.; Gretzki, P.; Niessen, M.; Bartels, T.; Reininghaus, M.


Journal of Laser Micro/Nanoengineering. Online journal 14 (2019), Nr.2, S.129-137
ISSN: 1880-0688
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
Fraunhofer ILT ()

High power ultrashort pulsed lasers are an ultimate manufacturing tool for a large variety of materials and provide outstanding properties for high precision manufacturing with almost no thermal effects and numerous new processing possibilities. However, using high power ultrashort pulsed lasers with high pulse repetition frequencies in the MHz region can cause thermal issues like overheating, melt generation and low ablation quality. High ablation quality only can be achieved, if all process parameters are carefully matched, which requires a deep understanding of the process, intensive simulation for selecting processing strategies and innovative system components. Beside ultra high speed scanning using polygon scanners the use of multiple laser beams provide the best and most versatile high power ablation solution. With switchable single beams using parallel acoustooptic and phase modulating beam steering systems together with diffractive optical beam splitter, high ablation rates can be achieved while maintaining the high processing quality. However, using multiple laser beams each single beam can influence the adjacent beam either by heat accumulation or by plasma and vapour emission. Distance of the single beams, pulse repetition frequency and scanning strategy have to be matched to the material and ablation geometry. With a careful adaption of all parameters highly accurate and fast processing can be achieved. With this approach a next step up to an all optical manufacturing system can be provided.