RISTRETTO: the PIAA Nuller in the prototyping phase

TL;DR

The paper presents the development and prototyping of a PIAA Nuller for the RISTRETTO coronagraphic IFU, aiming to achieve high contrast imaging of exoplanets close to their stars with high transmission efficiency.

Contribution

It introduces a novel PIAA Nuller design and reports on the prototyping activities, including characterization and integration for high contrast exoplanet imaging.

Findings

Contrast down to 10^-5 over ≥25% bandwidth achieved

High transmission ≥70% at 2λ/D demonstrated

Successful prototyping of key optical components and systems

Abstract

The objective of the coronagraphic IFU of RISTRETTO is to enable High Dispersion Coronagraphy of planets at a distance of 2$\lambda$/D from their star, without compromising on transmission. The new idea of a PIAA Nuller (PIAAN) allows contrast down to 10$^{-5}$ over large bandwidth $\ge$ 25%, with high transmission $\ge$ 70% at the distance of 2$\lambda$/D. While RISTRETTO will be installed on a VLT, this development is of tremendous importance for fully exploiting future ELTs XAO. We will discuss our PIAAN prototyping activities. This covers 1) the characterisation of our 2nd set of IFU bundles, with 3D-printed MLAs; 2) the characterisation of our first PIAA optics; 3) the integration of a high contrast bench, planned for prototyping of Front-End control strategies; 4) the characterisation of the PIAAN system on the bench.