The vector-apodizing phase plate coronagraph: design, current performance, and future development

TL;DR

The paper reviews the development, on-sky performance, and scientific results of the vector-apodizing phase plate coronagraph, highlighting its broadband capabilities, high efficiency, and applications in high-contrast imaging on large telescopes.

Contribution

It provides a comprehensive overview of the design, implementation, and performance of vAPP coronagraphs, including recent scientific results and future prospects.

Findings

High efficiency (>96%) in visible and infrared wavelengths.

Successful deployment in six instruments across four telescopes.

Enabled low-resolution spectroscopy (R~30) from 1 to 5 microns.

Abstract

Over the last decade, the vector-apodizing phase plate (vAPP) coronagraph has been developed from concept to on-sky application in many high-contrast imaging systems on 8-m class telescopes. The vAPP is an geometric-phase patterned coronagraph that is inherently broadband, and its manufacturing is enabled only by direct-write technology for liquid-crystal patterns. The vAPP generates two coronagraphic PSFs that cancel starlight on opposite sides of the point spread function (PSF) and have opposite circular polarization states. The efficiency, that is the amount of light in these PSFs, depends on the retardance offset from half-wave of the liquid-crystal retarder. Using different liquid-crystal recipes to tune the retardance, different vAPPs operate with high efficiencies ($>96\%$) in the visible and thermal infrared (0.55 $\mu$m to 5 $\mu$m). Since 2015, seven vAPPs have been installed in a total of six different instruments, including Magellan/MagAO, Magellan/MagAO-X, Subaru/SCExAO, and LBT/LMIRcam. Using two integral field spectrographs installed on the latter two instruments, these vAPPs can provide low-resolution spectra (R$\sim$30) between 1 $\mu$m and 5 $\mu$m. We review the design process, development, commissioning, on-sky performance, and first scientific results of all commissioned vAPPs. We report on the lessons learned and conclude with perspectives for future developments and applications.