24 August 2009 Dynamic array spot shaping for laser micro machining
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Abstract
Laser manufacturing of microstructures using a single focus is a well known technology. Multi-spot optics are applied for process parallelizing if the demand on throughput in mass production rises or large areas of material have to be processed. Diffractive optical elements (DOEs) are used for parallel laser processing of a repetitive structure. These elements split the beam into a periodic spot pattern, where each spot shows the same shape and energy. This allows simultaneous manufacturing of several equal shaped structures at the same time. For patterning a surface this is state of the art and the appropriate technique to reduce processing time while maintaining a high lateral resolution as well as a good relative positioning of the structure due to the DOE. We investigate the usage of microlens arrays as multifunctional elements for forming an arbitrary shaped laser beam into a spot-, a ring-spot- or a line-array pattern. It can be shown that the intensity distribution of each spot is equal to the intensity distribution of all other spots in the whole pattern. The shape of the spots is defined by the angular distribution of the incident beam. We demonstrate that besides other optical properties the output beam profile strongly depends on the Fresnel-Number and is influenced by diffraction and interference effects. We present important design rules which consider geometrical and physical optics. The properties of the spot arrays, like spot diameter, Rayleigh length and beam divergence in dependency of beam and system properties are investigated. Finally we will show some laser micro structuring and micro drilling results in different materials.
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A. Bich, K. J. Weible, R. Voelkel, M. Zimmermann, I. Harder, N. Lindlein, J. Masson, R. Bitterli, W. Noell, T. Scharf, "Dynamic array spot shaping for laser micro machining", Proc. SPIE 7430, Laser Beam Shaping X, 74300I (24 August 2009); doi: 10.1117/12.828435; https://doi.org/10.1117/12.828435
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