Dr. Helmut Schift
Paul-Scherrer-Institute, Micro- and Nanotechnology, Villigen PSI, Switzerland
»Polishing without touching – How to reduce roughness in refractive micro-optical elements«

Abstract:

Two-photon polymerization by direct laser writing enables to write refractive micro-optical ele-ments with sub-µm precision. The trajectories and layering during the direct writing process often result in roughness in the range of the writing increment, which has adverse effects for optical ap-plications. Instead of increasing overlap between adjacent voxels, roughness in the range of 100 nm can be smoothed-out by post-processing. For this a method known as TASTE was developed, which allows polishing of surfaces without changing the structural details or the overall shape. It works particularly well with thermoplastic polymers and enables sub-10 nm roughness. A process route was developed involving a copying step into PMMA, and applied to an array of concave microlenses.