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Lecture

Efficient ultra-short pulsed laser processing by dynamic SLM beam shaping for industrial use

Thursday (25.06.2020)
10:30 - 10:50 Room 3
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State of the art ultra-short pulse lasers are available with an average output power of up to a few hundred watts, promising more efficient laser processing. These high power ultra-short pulsed lasers are, in general, specified by high repetition rates in the range of several MHz, which, however, can result in adverse processing conditions like overheating, melt production and thus low ablation quality [1]. To reach a spatial pulse-to-pulse separation, and transmit the potential of high power ultra-short pulse lasers to efficient material ablation, high scanning speeds and multi-beam shaping technologies are two competing approaches. In contrast to static beam shaping with diffractive optical elements, dynamic beam shaping is a more flexible way for process-oriented beam shapes. Here, spatial light modulators (SLM) are used in many research areas, such as, e.g., wave front correction, spatial beam shaping and laser parallel processing [2]. Experiments have shown that the optimal fluence to ablate steels is under 1J/cm² [3]. Based on these results, it is necessary to use other beam profiles to achieve an efficient relation of available laser power and useful fluence. In this way, a SLM is a high flexible tool to generate arbitrary laser spot distributions. The combination of both, high power USP laser and SLM beam shaping, offers the chance to create an efficient roughing and finishing process with adapted tools.

 

In this report, we demonstrate the effect of different transversal beam shapes and the number of spots on the efficiency of stainless steel ablation processes. We employ an ultra-short pulse laser with an average power of up to 100W. The laser emits a wavelength of 1030nm with a pulse length of 800fs. The aim of the investigation is efficient area ablation in a multi pass process. To shape the laser beam, we use a cooled reflective based liquid crystal spatial light modulator. In particular, we present a comprehensive parameter study on multi beam ablation, optimised to maximum ablation rate. Our results show the effective ablation rates for the used beam profiles with the same laser power. As a result, that we can ablate twice as much material with the multi spot profile than a single spot.

 

Speaker:
Christian Lutz
University of Applied Science Aschaffenburg
Additional Authors:
  • Gian-Luca Roth
    University of Applied Science Aschaffenburg
  • Dr. Stefan Rung
    University of Applied Science Aschaffenburg
  • Prof. Dr. Ralf Hellmann
    University of Applied Science Aschaffenburg

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