Laboratory Demonstration of Spatial Linear Dark Field Control For Imaging Extrasolar Planets in Reflected Light
Abstract
Imaging planets in reflected light, a key focus of future NASA missions and extremely large telescopes, requires advanced wavefront control to maintain a deep, temporally correlated null of stellar halo—i.e., a dark hole (DH)—at just several diffraction beam widths. Using the Ames Coronagraph Experiment testbed, we present the first laboratory tests of Spatial Linear Dark Field Control (LDFC) approaching raw contrasts (∼5 × 10-7) and separations (1.5-5.2λ/D) needed to image Jovian planets around Sun-like stars with space-borne coronagraphs like WFIRST-CGI and image exo-Earths around low-mass stars with future ground-based 30 m class telescopes. In four separate experiments and for a range of different perturbations, LDFC largely restores (to within a factor of 1.2-1.7) and maintains a DH whose contrast is degraded by phase errors by an order of magnitude. Our implementation of classical speckle nulling requires a factor of 2-5 more iterations and 20-50 deformable mirror (DM) commands to reach contrasts obtained by spatial LDFC. Our results provide a promising path forward to maintaining DHs without relying on DM probing and in the low-flux regime, which may improve the duty cycle of high-contrast imaging instruments, increase the temporal correlation of speckles, and thus enhance our ability to image true solar system analogues in the next two decades.
- Publication:
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Publications of the Astronomical Society of the Pacific
- Pub Date:
- October 2020
- DOI:
- 10.1088/1538-3873/aba9ad
- arXiv:
- arXiv:2007.14413
- Bibcode:
- 2020PASP..132j4502C
- Keywords:
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- Astronomical instrumentation;
- Exoplanet detection methods;
- Exoplanets;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 13 pages, 7 figures, accepted for publication in Publications of the Astronomical Society of the Pacific