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Accounting for laser beam characteristics in the design of freeform optics for laser material processing

: Völl, Annika; Wester, Rolf; Berens, Michael; Buske, Paul; Stollenwerk, Jochen; Loosen, Peter


Advanced Optical Technologies 8 (2019), Nr.3-4, S.279-287
ISSN: 2192-8584
ISSN: 2192-8576
Fraunhofer ILT ()
beam shaping; freeform optics laser heat treatment; simulation

Recently, freeform optics have been introduced for application adapted beam shaping in laser heat treatment. There, intensity distributions are generated that induce previously defined temporal and spatial temperature profiles. To this end, a two-step simulation strategy is necessary, where in the first step the intensity distribution must be derived for which in the second step the freeform optics is calculated. To provide a design that can successfully be integrated in an experimental setup, the incoming laser beam’s characteristics must be accounted for in the derivation of the adapted intensity distribution as well as in the freeform optics design. Here, the two most relevant quantities are the beam’s maximum output power as well as the divergence angle. In this work, strategies are presented that account for the beam’s maximum output power in the derivation of the adapted intensity distribution. Furthermore, stabilizing methods are introduced to enhance the performance of a previously introduced freeform optics design algorithm that takes into account the laser beam’s finite divergence angle but suffers from numerical noise and oscillation problems. A simulation example that uses both techniques is given for (nano)ceramic thin-film laser processing.