Free form micro-optics enables uniform off-axis illumination and superposition of high power laser devices

Tanja Bizjak; Oliver Homburg; Andreas Bayer; Thomas Mitra; Lutz Aschke

doi:10.1117/12.794686

12 September 2008 Free form micro-optics enables uniform off-axis illumination and superposition of high power laser devices

Tanja Bizjak, Oliver Homburg, Andreas Bayer, Thomas Mitra, Lutz Aschke

Author Affiliations +

Proceedings Volume 7062, Laser Beam Shaping IX; 70620T (2008) https://doi.org/10.1117/12.794686
Event: Optical Engineering + Applications, 2008, San Diego, California, United States

Abstract

High power laser sources are used in a large variety of applications for material processing, such as ablation, welding, soldering, cutting, drilling, laser annealing, micro-machining and deep-UV lithography. Using high performance optics in the laser systems to generate the appropriate beam profile becomes a key factor for getting the best results and throughput in an application field. Refractive micro-lens arrays made of glass, semiconductors or crystals provide great advantages in laser applications, by improving efficiency, precision, intensity stability and performance. With LIMO's unique production technology, free form surfaces on monolithic arrays exceeding 200 mm edge length can be manufactured with high precision and reproducibility. Each lens of the array can be designed individually and can also be shaped asymmetrically. The asymmetric shape is defined by odd- and even-polynomial terms and/or an asymmetric cut-off from a polynomial surface. Advantages of asymmetric micro-lenses are off-axis light propagation, the correction of aberration effects, or the correction of the intensity profile deformations when the illuminated surfaces are not orthogonal to the optical axis. The applications results of such micro-lens arrays are presented for beam shaping of high power diode lasers. The generation of a homogeneous light field by a 100 W laser with tilted illumination under an angle of 30°-50° is shown. A multi-kW line generator based on the superposition of over 50 diode laser bars under different illumination angles is demonstrated as well. Novel microoptical beam shapers in lithographic applications reduce the complexity of macrooptics in hyper-NA illumination systems. Extremely uniform intensity distribution can be created without using field lenses or by using simple spherical field lenses instead of complex aspheres.

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Tanja Bizjak, Oliver Homburg, Andreas Bayer, Thomas Mitra, and Lutz Aschke "Free form micro-optics enables uniform off-axis illumination and superposition of high power laser devices", Proc. SPIE 7062, Laser Beam Shaping IX, 70620T (12 September 2008); https://doi.org/10.1117/12.794686

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