Implementing focal-plane phase masks optimized for real telescope apertures with SLM-based digital adaptive coronagraphy

TL;DR

This paper demonstrates the experimental validation of numerically optimized focal-plane phase masks, designed specifically for complex telescope apertures, using liquid crystal spatial light modulators to improve exoplanet imaging contrast.

Contribution

It introduces a novel experimental approach employing SLMs to implement optimized phase masks tailored for non-ideal telescope apertures.

Findings

Successful experimental validation of optimized phase masks

Enhanced contrast performance in simulated telescope conditions

Feasibility of adaptive SLM-based coronagraphy for complex apertures

Abstract

Direct imaging of exoplanets or circumstellar disk material requires extreme contrast at the 10-6 to 10-12 levels at < 100 mas angular separation from the star. Focal-plane mask (FPM) coronagraphic imaging has played a key role in this field, taking advantage of progress in Adaptive Optics on ground-based 8+m class telescopes. However, large telescope entrance pupils usually consist of complex, sometimes segmented, non-ideal apertures, which include a central obstruction for the secondary mirror and its support structure. In practice, this negatively impacts wavefront quality and coronagraphic performance, in terms of achievable contrast and inner working angle. Recent theoretical works on structured darkness have shown that solutions for FPM phase profiles, optimized for non-ideal apertures, can be numerically derived. Here we present and discuss a first experimental validation of this concept, using reflective liquid crystal spatial light modulators as adaptive FPM coronagraphs.