Polarization modeling and predictions for DKIST part 2: application of the Berreman calculus to spectral polarization fringes of beamsplitters and crystal retarders

David M. Harrington; Frans Snik; Christoph U. Keller; Stacey R. Sueoka; Gerard van Harten

doi:10.1117/1.JATIS.3.4.048001

27 October 2017 Polarization modeling and predictions for DKIST part 2: application of the Berreman calculus to spectral polarization fringes of beamsplitters and crystal retarders

David M. Harrington, Frans Snik, Christoph U. Keller, Stacey R. Sueoka, Gerard van Harten

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Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 3, Issue 4, 048001 (October 2017). https://doi.org/10.1117/1.JATIS.3.4.048001

Abstract

We outline polarization fringe predictions derived from an application of the Berreman calculus for the Daniel K. Inouye Solar Telescope (DKIST) retarder optics. The DKIST retarder baseline design used six crystals, single-layer antireflection coatings, thick cover windows, and oil between all optical interfaces. This tool estimates polarization fringes and optic Mueller matrices as functions of all optical design choices. The amplitude and period of polarized fringes under design changes, manufacturing errors, tolerances, and several physical factors can now be estimated. This tool compares well with observations of fringes for data collected with the spectropolarimeter for infrared and optical regions at the Dunn Solar Telescope using bicrystalline achromatic retarders as well as laboratory tests. With this tool, we show impacts of design decisions on polarization fringes as impacted by antireflection coatings, oil refractive indices, cover window presence, and part thicknesses. This tool helped DKIST decide to remove retarder cover windows and also recommends reconsideration of coating strategies for DKIST. We anticipate this tool to be essential in designing future retarders for mitigation of polarization and intensity fringe errors in other high spectral resolution astronomical systems.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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David M. Harrington, Frans Snik, Christoph U. Keller, Stacey R. Sueoka, and Gerard van Harten "Polarization modeling and predictions for DKIST part 2: application of the Berreman calculus to spectral polarization fringes of beamsplitters and crystal retarders," Journal of Astronomical Telescopes, Instruments, and Systems 3(4), 048001 (27 October 2017). https://doi.org/10.1117/1.JATIS.3.4.048001

Received: 10 July 2017; Accepted: 3 October 2017; Published: 27 October 2017

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