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Proceedings Paper • Open Access

Uniformity and wavefront control of optical filters
Author(s): Michael Vergöhl; Chris Britze; Stefan Bruns; Andreas Pflug; Jennifer Zimara; Bernd Schäfer; Klaus Mann; Volker Kirschner

Paper Abstract

The present paper addresses uniformity effects in demanding dielectric optical coatings. The origins of spectral resonant wavefront errors (WFE) induced by non-uniformities in complex dielectric filters are investigated in detail. The coating is a broad-band beamsplitter with a high reflectance between 400 and 900 nm and a high transmittance between 920 and 2300nm. The WFE can significantly be reduced with an optimized design. A new setup based on Hartmann-Shack sensors measures the spectrally dependent WFE in the visual spectral range. The paper presents a method for referencing the measured data. The experimental WFE maps obtained by spectral Hartmann-Shack measurements agree well with the expected spectra taken from spectral photometric measurements and the coating design. The paper also addresses coatings on curved surfaces. A band pass filter centered at 670 nm on the convex side of a lens was developed. Using a combination of a sub-rotation and special uniformity masks, a very low spectral shift of the passband position overall the lens surface could be demonstrated. The deposition concept and mask design, respectively, are developed via simulation studies based on a simulation approach shown in [10]. Extension of the model framework by plasma simulation and a concept for computing deposition profiles on moving 3D substrates was required for solving the problem.

Paper Details

Date Published: 12 July 2019
PDF: 11 pages
Proc. SPIE 11180, International Conference on Space Optics — ICSO 2018, 1118046 (12 July 2019); doi: 10.1117/12.2536069
Show Author Affiliations
Michael Vergöhl, Fraunhofer Institute for Surface Engineering and Thin Films (Germany)
Chris Britze, Fraunhofer Institute for Surface Engineering and Thin Films (Germany)
Stefan Bruns, Fraunhofer Institute for Surface Engineering and Thin Films (Germany)
Andreas Pflug, Fraunhofer Institute for Surface Engineering and Thin Films (Germany)
Jennifer Zimara, Laser-Lab. Göttingen e.V. (Germany)
Bernd Schäfer, Laser-Lab. Göttingen e.V. (Germany)
Klaus Mann, Laser-Lab. Göttingen e.V. (Germany)
Volker Kirschner, European Space Research and Technology Ctr. (Netherlands)

Published in SPIE Proceedings Vol. 11180:
International Conference on Space Optics — ICSO 2018
Zoran Sodnik; Nikos Karafolas; Bruno Cugny, Editor(s)

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