Mid-IR AGPMs for ELT applications

TL;DR

This paper discusses the design and expected performance of mid-infrared Annular Groove Phase Masks (AGPMs) made on diamond substrates, aimed at enhancing exoplanet detection with the E-ELT/METIS instrument.

Contribution

It presents optimized designs and performance expectations for mid-IR AGPMs on diamond, tailored for ELT applications, advancing coronagraph technology.

Findings

Optimized mid-IR AGPM designs for diamond substrates.

Expected high starlight suppression performance.

Suitability for E-ELT/METIS exoplanet imaging.

Abstract

The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument.