31 research outputs found
Fully broadband vAPP coronagraphs enabling polarimetric high contrast imaging
We present designs for fully achromatic vector Apodizing Phase Plate (vAPP)
coronagraphs, that implement low polarization leakage solutions and achromatic
beam-splitting, enabling observations in broadband filters. The vAPP is a pupil
plane optic, inducing the phase through the inherently achromatic geometric
phase. We discuss various implementations of the broadband vAPP and set
requirements on all the components of the broadband vAPP coronagraph to ensure
that the leakage terms do not limit a raw contrast of 1E-5. Furthermore, we
discuss superachromatic QWPs based of liquid crystals or quartz/MgF2
combinations, and several polarizer choices. As the implementation of the
(broadband) vAPP coronagraph is fully based on polarization techniques, it can
easily be extended to furnish polarimetry by adding another QWP before the
coronagraph optic, which further enhances the contrast between the star and a
polarized companion in reflected light. We outline several polarimetric vAPP
system designs that could be easily implemented in existing instruments, e.g.
SPHERE and SCExAO.Comment: 11 pages, 5 figures, presented at SPIE Astronomical Telescopes and
Instrumentation 201
Minimizing the polarization leakage of geometric-phase coronagraphs with multiple grating pattern combinations
The design of liquid-crystal diffractive phase plate coronagraphs for
ground-based and space-based high-contrast imaging systems is limited by the
trade-off between spectral bandwidth and polarization leakage. We demonstrate
that by combining phase patterns with a polarization grating (PG) pattern
directly followed by one or several separate PGs, we can suppress the
polarization leakage terms by additional orders of magnitude by diffracting
them out of the beam. \textcolor{black}{Using two PGs composed of a
single-layer liquid crystal structure in the lab, we demonstrate a leakage
suppression of more than an order of magnitude over a bandwidth of 133 nm
centered around 532 nm. At this center wavelength we measure a leakage
suppression of three orders of magnitude.} Furthermore, simulations indicate
that a combination of two multi-layered liquid-crystal PGs can suppress leakage
to for 1-2.5 m and for 650-800 nm. We introduce
multi-grating solutions with three or more gratings that can be designed to
have no separation of the two circular polarization states, and offer even
deeper suppression of polarization leakage. We present simulations of a
triple-grating solution that has leakage on the first Airy ring
from 450 nm to 800 nm. We apply the double-grating concept to the Vector-Vortex
coronagraph of charge 4, and demonstrate in the lab that polarization leakage
no longer limits the on-axis suppression for ground-based contrast levels.
Lastly, we report on the successful installation and first-light results of a
double-grating vector Apodizing Phase Plate pupil-plane coronagraph installed
at the Large Binocular Telescope. We discuss the implications of these new
coronagraph architectures for high-contrast imaging systems on the ground and
in space.Comment: 23 pages, 15 figures, accepted for publication in PAS
APLC-Optimization: an apodized pupil Lyot coronagraph design survey toolkit
We present a publicly available software package developed for exploring
apodized pupil Lyot coronagraph (APLC) solutions for various telescope
architectures. In particular, the package optimizes the apodizer component of
the APLC for a given focal-plane mask and Lyot stop geometry to meet a set of
constraints (contrast, bandwidth etc.) on the coronagraph intensity in a given
focal-plane region (i.e. dark zone). The package combines a high-contrast
imaging simulation package HCIPy with a third-party mathematical optimizer
(Gurobi) to compute the linearly optimized binary mask that maximizes
transmission. We provide examples of the application of this toolkit to several
different telescope geometries, including the Gemini Planet Imager (GPI) and
the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed.
Finally, we summarize the results of a preliminary design survey for the case
of a 6~m aperture off-axis space telescope, as recommended by the 2020 NASA
Decadal Survey, exploring APLC solutions for different segment sizes. We then
use the Pair-based Analytical model for Segmented Telescope Imaging from Space
(PASTIS) to perform a segmented wavefront error tolerancing analysis on these
solutions.Comment: 17 pages, 16 figures, SPIE conferenc
High contrast imaging with ELT/METIS: The wind driven halo, from SPHERE to METIS
International audienceMETIS is one of the three first-light instruments planned for the ELT, mainly dedicated to high contrast imaging in the mid-infrared. On the SPHERE high-contrast instrument currently installed at the VLT, we observe that one of the main contrast limitations is the wind driven halo, due to the limited AO running speed with respect to the atmospheric turbulence temporal evolution. From this observation, we extrapolate this signature to the ELT/METIS instrument, which is equipped with a single conjugated adaptive optics system and with several coronagraphic devices. By making use of an analytic AO simulator, we compare the amount of wind driven halo observed with SPHERE and with METIS, under the same turbulence conditions
Integrated photonic-based coronagraphic systems for future space telescopes
The detection and characterization of Earth-like exoplanets around Sun-like
stars is a primary science motivation for the Habitable Worlds Observatory.
However, the current best technology is not yet advanced enough to reach the
10^-10 contrasts at close angular separations and at the same time remain
insensitive to low-order aberrations, as would be required to achieve
high-contrast imaging of exo-Earths. Photonic technologies could fill this gap,
potentially doubling exo-Earth yield. We review current work on photonic
coronagraphs and investigate the potential of hybridized designs which combine
both classical coronagraph designs and photonic technologies into a single
optical system. We present two possible systems. First, a hybrid solution which
splits the field of view spatially such that the photonics handle light within
the inner working angle and a conventional coronagraph that suppresses
starlight outside it. Second, a hybrid solution where the conventional
coronagraph and photonics operate in series, complementing each other and
thereby loosening requirements on each subsystem. As photonic technologies
continue to advance, a hybrid or fully photonic coronagraph holds great
potential for future exoplanet imaging from space.Comment: Conference Proceedings of SPIE: Techniques and Instrumentation for
Detection of Exoplanets XI, vol. 12680 (2023