High Contrast Demonstrations of Novel Scalar Vortex Coronagraph Designs at the High Contrast Spectroscopy Testbed

TL;DR

This paper evaluates scalar vortex coronagraphs (SVCs) for exoplanet imaging, demonstrating their potential with promising contrast levels and chromatic performance in laboratory tests, offering an alternative to vector vortex coronagraphs.

Contribution

It presents the first experimental testing of stepped SVC masks on a high-contrast testbed, showing their effectiveness and potential for future exoplanet imaging missions.

Findings

Achieved raw contrasts of ~1e-5 at 7-9 lambda/D

Characterized chromatic performance of SVCs

Reached contrasts of ~1e-7 with wavefront control

Abstract

For direct imaging of exoplanets, Scalar Vortex Coronagraphs (SVCs) are an attractive alternative to the popularly used Vector Vortex Coronagraphs (VVCs). This is primarily because they are able to induce the same phase ramp regardless of the incoming light's polarization state. We tested a set of stepped SVC staircase masks in the Exoplanet Technology Laboratory (ET Lab) at Caltech on the High-Contrast Spectroscopy Testbed (HCST). Here we present some preliminary findings of their starlight suppression ability, achieving raw contrasts on the order of 1e-5 for 7 to 9 lambda/D. We also characterized their chromatic performance and performed wavefront control to achieve preliminary contrasts on the order of 1e-7 with EFC. These initial experimental results with SVCs have shown scalar vortex technology has a great potential for future exoplanet direct imaging missions.