Apodized phase mask coronagraphs for arbitrary apertures. II. Comprehensive review of solutions for the vortex coronagraph

Abstract

With a clear circular aperture, the vortex coronagraph perfectly cancels an on-axis point source and offers a 0.9 or 1.75 lambda/D inner working angle for topological charge 2 or 4, respectively. Current and near-future large telescopes are on-axis, however, and the diffraction effects of the central obscuration, and the secondary supports are strong enough to prevent the detection of companions 1e-3 - 1e-5 as bright as, or fainter than, their host star. Recent advances show that a ring apodizer can restore the performance of this coronagraph by compensating for the diffraction effects of a circular central obscuration in a 1D modeling of the pupil. We extend this work and optimize apodizers for arbitrary apertures in 2D in order to tackle the diffraction effects of the spiders and other noncircular artefacts in the pupil. We use a numerical optimization scheme to compute hybrid coronagraph designs that combine the advantages of the vortex coronagraph (small in IWA) and of shaped pupils coronagraphs (robustness to central obscuration and pupil asymmetric structures). We maximize the apodizer transmission, while constraints are set on the extremum values of the electric field that is computed in chosen regions of the Lyot plane through closed form expressions. Optimal apodizers are computed for topological charges 2 and 4 vortex coronagraphs and for telescope apertures with 10-30% central obscurations and 0-1% thick spiders. We characterize the impacts of the obscuration ratio and the thickness of the spiders on the throughput and the IWA for the two topological charges.

23 pages, 12 figures, 2 tables

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Cited by in corpus (14)

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• Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph
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• Apodized vortex coronagraph designs for segmented aperture telescopes
• Apodization in high-contrast long-slit spectroscopy. II. Concept validation and first on-sky results with VLT/SPHERE
• Active correction of aperture discontinuities (ACAD) for space telescope pupils: a parametic analysis
• Vortex coronagraphy from self-engineered liquid crystal spin-orbit masks
• High-contrast Demonstration of an Apodized Vortex Coronagraph
• Fast Linearized Coronagraph Optimizer (FALCO) IV. Coronagraph design survey for obstructed and segmented apertures
• Analysis of nulling phase functions suitable to image plane coronagraphy
• Redundant apodization for direct imaging of exoplanets I: Robustness to primary mirror segmentation-induced errors outside the segment diffraction limit
• Redundant apodization for direct imaging of exoplanets 2: Application to island effects
• Correcting for the effects of pupil discontinuities with the ACAD method
• Interferometric apodization by homothety -- II. Experimental validation