Design and manufacturing of a multi-zone phase-shifting coronagraph mask for extremely large telescopes
- Others:
- Joseph Louis LAGRANGE (LAGRANGE) ; Université Nice Sophia Antipolis (1965 - 2019) (UNS) ; COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur ; COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
- Laboratoire d'Astrophysique de Marseille (LAM) ; Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
- UMI GT CNRS ; Georgia Institute of Technology [Atlanta]-Centre National de la Recherche Scientifique (CNRS)
Description
Context. High-contrast imaging of exoplanets around nearby stars with future large-segmented apertures requires starlight suppression systems optimized for complex aperture geometries. Future extremely large telescopes (ELTs) equipped with high-contrast instruments operating as close as possible to the diffraction limit will open a bulk of targets in the habitable zone around M-stars. In this context, the phase-induced amplitude apodization complex mask coronagraph (PIAACMC) is a promising concept for high-efficiency coronagraphic imaging at small angular separations with segmented telescopes.Aims. The complex focal plane mask of the PIAACMC is a multi-zone, phase-shifting mask comprised of tiled hexagons that vary in depth. The mask requires micro-fabrication techniques because it is generally made of hundreds micron-scale hexagonal zones with depths ranging over a few microns. We aim to demonstrate that the complex focal plane mask of a PIAACMC with a small inner working angle can be designed and manufactured for segmented apertures.Methods. We report on the numerical design, specifications, manufacturing, and characterization of a PIAACMC complex focal plane mask for the segmented pupil experiment for exoplanet detection facility.Results. Our PIAACMC design offers an inner working angle of 1.3 λ/D and is optimized for a 30% telescope-central-obscuration ratio including six secondary support structures (ESO/ELT design). The fabricated reflective focal plane mask is made of 499 hexagons, and the characteristic size of the mask features is 25 μm, with depths ranging over ±0.4 μm. The mask sag local deviation is measured to an average error of 3 nm and standard deviation of 6 nm rms. The metrological analysis of the mask using interferential microscopy gives access to an in-depth understanding of the component's optical quality, including a complete mapping of the zone depth distribution zone-depth distribution. The amplitude of the errors in the fabricated mask are within the wavefront control dynamic range.Conclusions. We demonstrate the feasibility of fabricating and characterizing high-quality PIAA complex focal plane masks.
Abstract
International audience
Additional details
- URL
- https://hal.archives-ouvertes.fr/hal-02899005
- URN
- urn:oai:HAL:hal-02899005v1
- Origin repository
- UNICA