Lord of the Ring Gratings: Their use as image plane filters for coronagraphy

TL;DR

This paper investigates circular amplitude and phase gratings as innovative image plane filters for coronagraphy, demonstrating their potential to achieve high starlight attenuation for exoplanet imaging.

Contribution

It introduces a novel inversion approach to classical Lyot coronagraphs using circular gratings and evaluates their performance through theoretical analysis and simulations.

Findings

High starlight attenuation ratios are achievable with optimized systems.

Circular gratings can serve as effective image plane filters in coronagraphs.

Numerical simulations identify the most promising grating designs.

Abstract

Coronagraphy is an efficient technique for identifying and characterizing extra-solar planets orbiting in the habitable zone of their parent star. An important family of coronagraphs is based on amplitude or phase filters placed at an intermediate image plane of the optical system, spreading starlight outside of the so-called Lyot stop located at the exit pupil plane of the instrument. This article explores the potential of circular amplitude and phase gratings employed as image plane coronagraph filters. It presents a theoretical analysis of the simplest case of an amplitude circular grating and introduces an inversion paradigm with respect to classical Lyot coronagraph, by exchanging its image and pupil masks. Various types of circular gratings are considered and their performance is evaluated with the help of numerical simulations. The most promising solutions are presented. We conclude that high attenuation ratios of the starlight are feasible, provided that the system has been carefully optimized