Shaped Pupil Lyot Coronagraphs: High-Contrast Solutions for Restricted Focal Planes

TL;DR

This paper introduces a hybrid shaped pupil Lyot coronagraph architecture that uses binary masks for high-contrast imaging, optimizing starlight suppression for exoplanet and debris disk observations.

Contribution

It presents a novel hybrid design replacing the apodizer with a shaped pupil mask and introduces joint optimization of the Lyot stop and apodizer for improved performance.

Findings

High transmission shaped pupil masks outperform gray apodizers for restricted contrast regions.

Joint optimization of Lyot stop and apodizer enhances starlight suppression.

Designed SPLC architectures support WFIRST-AFTA's exoplanet and debris disk science goals.

Abstract

Coronagraphs of the apodized pupil and shaped pupil varieties use the Fraunhofer diffraction properties of amplitude masks to create regions of high contrast in the vicinity of a target star. Here we present a hybrid coronagraph architecture in which a binary, hard-edged shaped pupil mask replaces the gray, smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast and bandwidth goal in this configuration, as long as the prescribed region of contrast is restricted to a finite area in the image, a shaped pupil is the apodizer with the highest transmission. We relate the starlight cancellation mechanism to that of the conventional APLC. We introduce a new class of solutions in which the amplitude profile of the Lyot stop, instead of being fixed as a padded replica of the telescope aperture, is jointly optimized with the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs for the baseline architecture of the Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA) coronagraph. These SPLCs help to enable two scientific objectives of the WFIRST-AFTA mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in reflected starlight and (2) debris disk imaging.