How post-processing by selective thermal reflow can reduce the roughness of 3D lithography in micro-optical lenses

Robert Kirchner; Nachiappan Chidambaram; Mirco Altana; Helmut Schift

doi:10.1117/12.2258090

24 February 2017 How post-processing by selective thermal reflow can reduce the roughness of 3D lithography in micro-optical lenses

Robert Kirchner, Nachiappan Chidambaram, Mirco Altana, Helmut Schift

Author Affiliations +

Proceedings Volume 10095, Laser 3D Manufacturing IV; 1009507 (2017) https://doi.org/10.1117/12.2258090
Event: SPIE LASE, 2017, San Francisco, California, United States

Abstract

Most polymeric refractive micro-optics simultaneously demand ultra-smooth 3D topographies and precise geometry for high optical performance and low stray light. We have established a surface selective smoothening for thermoplastic polymers that does not affect the designed optical geometry. For example, high curvature corners required for a 50 μm tall optical diffuser device were maintained while the surface roughness was reduced to about 10 nm RMS. 3D master structures were fabricated using direct write laser-lithography with two-photon absorption. Master structures were then replicated into poly(methyl methacrylate) through a poly(dimethyl siloxane) intermediate copying step and subsequently smoothed-out by high-energy photon exposure and thermal post-processing. The smoothening results in a lower roughness compared to a direct writing strategy using even about 50 nm vertical discretization steps still enables 10 times faster writing times.

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Citation Download Citation

Robert Kirchner, Nachiappan Chidambaram, Mirco Altana, and Helmut Schift "How post-processing by selective thermal reflow can reduce the roughness of 3D lithography in micro-optical lenses", Proc. SPIE 10095, Laser 3D Manufacturing IV, 1009507 (24 February 2017); https://doi.org/10.1117/12.2258090

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