Dimpled scalar vortex coronagraph laboratory demonstration

TL;DR

This paper demonstrates advanced scalar vortex coronagraph prototypes with radial phase dimples, achieving high-contrast imaging across narrow and broadband spectra, advancing space-based exoplanet imaging technology.

Contribution

Introduces second-generation dimpled scalar vortex masks that improve broadband starlight suppression and match predicted performance, advancing coronagraph design.

Findings

Achieved the best in-air contrasts for scalar vortex masks to date.

Dimpled vortex performance matches predictions within a factor of two.

Demonstrated high-contrast imaging across 2%, 10%, and 18% bandwidths.

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.