Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) on-sky demonstration with MagAO-X^★

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
² Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ, USA
³ Wyant College of Optical Sciences, The University of Arizona, 1630 E University Blvd, Tucson, AZ, USA
⁴ Subaru Telescope, National Observatory of Japan, National Institutes of Natural Sciences, 650 N. A’ohoku Place, Hilo, Hawaii, USA
⁵ Astrobiology Center, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo, Japan
⁶ Northrop Grumman Corporation, 600 South Hicks Road, Rolling Meadows, IL, USA
⁷ Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY, USA
⁸ Draper Laboratory, 555 Technology Square, Cambridge, MA, USA
⁹ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
¹⁰ Starfire Optical Range, Kirtland Air Force Base, Albuquerque, NM, USA

^★★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 28 October 2025
Accepted: 20 February 2026

Abstract

Advancing the technological development of small inner working angle (IWA) coronagraphs is essential to enabling high-contrast imaging of temperate exoplanets with future extremely large telescopes (ELTs). The PIAACMC has been shown to closely approach the theoretical limit for coronagraphic throughput but its performance has not been fully characterised on-sky. This study serves as the first on-sky characterisation of contrast and IWA performance of the PIAACMC. We also performed a technological demonstration of the PIAACMC at sub-micron nearinfrared (NIR) wavelengths approaching the visible. We designed and manufactured phase-shifting focal plane masks for the PIAACMC. These were optimised for two cases, a narrowband 875 filter (875 nm, ∼3% bandwidth) and a broadband z′ filter (908 nm, ∼14% bandwidth). We tested the coronagraphs both with an internal source and on-sky using MagAO-X, the extreme adaptive optics (XAO) instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory, Chile. We show good recovery of the off-axis light’s point spread function (PSF) shape both with the internal source (within ∼92% and ∼97% depending on the separation) and on-sky when aligning the inverse set of PIAA lenses. We demonstrate sub-λ/D IWAs with the instrument’s internal source of about 0.74 λ/D with the 875 filter and 0.76 λ/D with the z’ filter. We reach average raw contrasts within 1 and 5 λ/D with the internal source of about 1.6 × 10⁻³ with the 875 filter and 1.3 × 10⁻³ with the z’ filter. These are mainly limited by the focal plane mask manufacturing errors, jitter, and residual quasi-static speckles in MagAO-X. We also show on-sky average raw contrasts within 1 and 5 λ/D of about 1.4 × 10⁻² with the 875 filter and 7.8 × 10⁻³ with the z’ filter. These are likely limited by wavefront control, low-order aberrations, and poor observing conditions. We have successfully characterised PIAACMC’s performance and demonstrated its technology on-sky for the first time at sub-micron wavelengths. Future work will improve the design and manufacturing processes of the focal plane masks to improve robustness and reach deeper contrast, as well as integrate focal plane wavefront control for non-common path aberrations (NCPAs) correction.