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Proceedings Paper

Microlens laser beam homogenizer: from theory to application
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Paper Abstract

Many applications in laser manufacturing like semiconductor lithography, micro-machining, micro-structuring or material-analysis require a homogeneous intensity distribution of the laser beam over its complete profile. Refractive and diffractive beam homogenizer solutions have been developed for this challenge, but their applicability strongly depends on the physics of the individual laser beam. This paper investigates the influence of laser beam properties like spatial coherence for microlens beam homogenizers. Diffraction at the small lens apertures and interference effects of periodic arrays are explained by using diffraction theory. Different microlens beam homogenizer configurations are presented. Design considerations that might be helpful for the layout of a specific microlens beam homogenizer system are discussed. It is shown that, among other factors, the Fresnel number is the most important quantity to characterize the influence of diffraction effects on microlens laser beam homogenizers. The influence of the spatial partial coherence will be explained for the example of a Fly's eye condenser. For cw laser sources, the influence of a rotating diffuser plate on grating interference and speckles effects is investigated. Finally, the theory will be compared to some practical examples in planar laser measurement techniques, in combustion diagnostics and micromachining with Excimer lasers.

Paper Details

Date Published: 26 September 2007
PDF: 13 pages
Proc. SPIE 6663, Laser Beam Shaping VIII, 666302 (26 September 2007); doi: 10.1117/12.731391
Show Author Affiliations
Maik Zimmermann, Bayerisches Laserzentrum GmbH (Germany)
Norbert Lindlein, Institute of Optics, Information and Photonics, Univ. of Erlangen (Germany)
Reinhard Voelkel, SUSS MicroOptics SA (Switzerland)
Kenneth J. Weible, SUSS MicroOptics SA (Switzerland)

Published in SPIE Proceedings Vol. 6663:
Laser Beam Shaping VIII
Fred M. Dickey; David L. Shealy, Editor(s)

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