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Proceedings Paper

Scalar vortex coronagraph mask design and predicted performance
Author(s): Garreth Ruane; Dimitri Mawet; A.J. Eldorado Riggs; Eugene Serabyn
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Paper Abstract

Vortex coronagraphs are an attractive solution for imaging exoplanets with future space telescopes due to their relatively high throughput, large spectral bandwidth, and low sensitivity to low-order aberrations compared to other coronagraphs with similar inner working angles. Most of the vortex coronagraph mask development for space applications has focused on generating a polychromatic, vectorial, optical vortex using multiple layers of liquid crystal polymers. While this approach has been the most successful thus far, current fabrication processes achieve retardance errors of 0.1-1.0°, which causes a nonnegligible fraction of the starlight to leak through the coronagraph. Circular polarizers are typically used to reject the stellar leakage reducing the throughput by a factor of two. Vector vortex masks also complicate wavefront control because they imprint conjugated phase ramps on the orthogonal circular polarization components, which may need to be split in order to properly sense and suppress the starlight. Scalar vortex masks can potentially circumvent these limitations by applying the same phase shift to all incident light regardless of the polarization state and thus have the potential to significantly improve the performance of vortex coronagraphs. We present scalar vortex coronagraph designs that make use of focal plane masks with multiple layers of dielectrics that (a) produce phase patterns that are relatively friendly to standard manufacturing processes and (b) achieve sufficient broadband starlight suppression, in theory, for imaging Earth-like planets with future space telescopes.

Paper Details

Date Published: 9 September 2019
PDF: 16 pages
Proc. SPIE 11117, Techniques and Instrumentation for Detection of Exoplanets IX, 111171F (9 September 2019); doi: 10.1117/12.2528625
Show Author Affiliations
Garreth Ruane, Jet Propulsion Lab. (United States)
Caltech (United States)
Dimitri Mawet, Caltech (United States)
Jet Propulsion Lab. (United States)
A.J. Eldorado Riggs, Jet Propulsion Lab. (United States)
Eugene Serabyn, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 11117:
Techniques and Instrumentation for Detection of Exoplanets IX
Stuart B. Shaklan, Editor(s)

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