Minimizing interference in microlens array homogenizer for a coherent UV laser

Sten A. Lindau

doi:10.1117/12.929686

15 October 2012 Minimizing interference in microlens array homogenizer for a coherent UV laser

Sten A. Lindau

Proceedings Volume 8490, Laser Beam Shaping XIII; 84900G (2012) https://doi.org/10.1117/12.929686
Event: SPIE Optical Engineering + Applications, 2012, San Diego, California, United States

Abstract

A Gaussian to top-hat beam homogenizer has been designed and fabricated for a UV laser illumination system used in the manufacture of integrated circuit substrates. An important part of the system is a “coherence buster” which is used for minimizing interference effects, normally encountered when using microlens array homogenizers together with a coherent light source. The coherence buster is a diffraction grating, which introduces a time delay across the beam. If this time delay is sufficiently large in comparison to the pulse length, it can be so arranged that beams, which would normally interfere, now arrives at different times and therefore add incoherently. The theory behind the coherence reduction is described, as well as the design of the grating. The irradiance uniformity of the manufactured homogenizer has been measured, and shown to be free from interference fringes.

Citation Download Citation

Sten A. Lindau "Minimizing interference in microlens array homogenizer for a coherent UV laser", Proc. SPIE 8490, Laser Beam Shaping XIII, 84900G (15 October 2012); https://doi.org/10.1117/12.929686

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