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arXiv · 2603.22551

Dimpled scalar vortex coronagraph laboratory demonstration

Niyati Desai·Garreth Ruane·Susan Redmond·Dimitri Mawet·Eugene Serabyn·Bertrand Mennesson
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Abstract

Achieving the Habitable Worlds Observatory (HWO) goal of 10^-10 contrast at a separation of 3 $\lambda$/D across a 20% bandwidth requires coronagraph focal plane masks with both broadband high contrast performance and high planet throughput. Scalar vortex coronagraphs (SVCs) offer a promising alternative to polarization-sensitive vector vortex designs but face chromatic limitations. This work presents the latest laboratory demonstrations of second-generation scalar vortex prototypes that incorporate radial phase dimples to improve broadband starlight suppression. We compare these new "dimpled" sawtooth masks to previous-generation scalar designs through high-contrast imaging experiments on the In-Air Coronagraph Testbed. Using electric field conjugation, we achieve near testbed-limited contrasts across both narrow (2%) and broadband (10%) spectral ranges. We report the best in-air contrasts achieved to date for scalar vortex masks across narrow and broadband spectral ranges and we also show that the dimpled vortex predicted bench-limited contrast performances for 2%, 10% and 18% bandwidths agree with the measured lab contrasts within a factor of two. These results highlight the potential of topographically achromatized scalar vortex masks as candidates for future space-based high-contrast imaging missions and mark a significant step toward polarization-independent coronagraphs capable of meeting HWO performance requirements.

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Niyati Desai, Garreth Ruane, Susan Redmond, Dimitri Mawet, Eugene Serabyn, Bertrand Mennesson. 2026-03-23. Dimpled scalar vortex coronagraph laboratory demonstration. https://doi.org/10.1117/1.jatis.12.4.041006

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