GPI 2.0: Optical Designs for the Upgrade of the Gemini Planet Imager Coronagraphic system

TL;DR

This paper presents new optical designs for the GPI 2.0 upgrade, improving contrast and throughput of the coronagraph system using an optimization software, preparing for on-sky deployment in 2023.

Contribution

The paper introduces novel apodizer and Lyot stop designs for GPI 2.0, utilizing a new optimization software to enhance performance metrics.

Findings

Achieved better raw contrast at the dark zone's inner working angle.

Improved core throughput while maintaining robustness to misalignment.

Designs are ready for on-sky use in 2023.

Abstract

The Gemini Planet Imager (GPI) is an integral field spectrograph (IFS) and coronagraph that is one of the few current generation instruments optimized for high-contrast direct imaging of substellar companions. The instrument is in the process of being upgraded and moved from its current mount on the Gemini South Observatory in Cerro Pachon, Chile, to its twin observatory, Gemini North, on Mauna Kea (a process colloquially dubbed 'GPI 2.0'). We present the designs that have been developed for the part of GPI 2.0 that pertains to upgrading various optical components of the GPI coronagraphic system. More specifically, we present new designs for the apodizer and Lyot stop (LS) that achieve better raw contrast at the inner working angle of the dark zone as well as improved core throughput while retaining a similar level of robustness to LS misalignment. To generate these upgraded designs, we use our own publicly available software package called APLC-Optimization that combines a commercial linear solver (Gurobi) with a high contrast imaging simulation package (HCIPy) in order to iteratively propagate light through a simulated model of an apodized phase lyot coronagraph (APLC), optimizing for the best coronagraph performance metrics. The designs have recently finished being lithographically printed by a commercial manufacturer and will be ready for use when GPI 2.0 goes on-sky in 2023.