Active focal-plane coronagraphy with liquid-crystal spatial-light modulators: Broadband contrast performance in the visible

TL;DR

This paper demonstrates that liquid-crystal spatial-light modulators can serve as effective broadband active focal-plane phase masks in visible light, enabling high-contrast astronomical imaging with minimal performance loss across a wide spectral range.

Contribution

It provides the first laboratory validation of broadband performance of commercially-available SLMs as active focal-plane coronagraphic masks in the visible spectrum.

Findings

Contrast performance remains high across ~12% bandwidth in laboratory tests.

SLMs effectively function as broadband phase masks under realistic telescope conditions.

Potential for adaptive high-contrast imaging in ground-based astronomy is demonstrated.

Abstract

The technological progress in spatial-light modulators (SLM) technology has made it possible to use those devices as programmable active focal-plane phase coronagraphic masks, opening the door to novel versatile and adaptive high-contrast imaging observation strategies. However, the scalar nature of the SLM-induced phase response is a potential hurdle when applying the approach to wideband light, as is typical in astronomical imaging. For the first time, we present laboratory results with broadband light (up to ~12pc bandwidth) for two commercially-available SLM devices used as active focal-plane phase masks in the visible regime (640 nm). It is shown that under ideal or realistic telescope aperture conditions, the contrast performance is negligibly affected in this bandwidth regime, reaching sufficient level for ground-based high-contrast imaging, which is typically dominated by atmospheric residuals.