Benefits of adding radial phase dimples on scalar coronagraph phase masks

TL;DR

This paper explores how adding radial phase dimples to scalar coronagraph phase masks can significantly enhance broadband performance by reducing chromatic stellar leakage, without increasing sensitivity to low-order aberrations.

Contribution

It introduces hybrid scalar vortex masks with radial phase dimples, demonstrating improved broadband contrast performance in coronagraphs.

Findings

Radial phase dimples improve broadband contrast.

Adding dimples does not increase low-order aberration sensitivity.

Suppression of central leakage enhances performance without restoring aberration sensitivities.

Abstract

Current scalar coronagraph focal plane mask designs are performance-limited by chromaticity. We investigate the effects of adding central Roddier and dual zone phase dimples to scalar vortex masks to improve broadband performance by suppressing the chromatic stellar leakage. We present hybrid designs with radial phase dimples integrated with the sawtooth vortex, wrapped vortex, and cosine phase mask. We show that using these dimples, it is possible to substantially improve the broadband contrast performance of scalar phase masks. We also show that although adding a phase dimple does not increase the sensitivity to low-order aberrations, suppressing the central leakage of scalar vortex coronagraphs does not restore the aberrations sensitivities to their notional state.