Dimpled scalar vortex coronagraph laboratory demonstration for the Habitable Worlds Observatory

Achieving the Habitable Worlds Observatory (HWO) goal of $10^{-10}$ contrast across a $\ge$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 phase metrology, microscope inspection, and 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 also show that the dimpled vortex lab and predicted bench-limited contrast performances for 2\%, 10\% and 18\% bandwidths agree within a factor of two, marking a significant step toward polarization-independent coronagraphs capable of meeting HWO performance requirements.