Laboratory Demonstration of Spatial Linear Dark Field Control For Imaging Extrasolar Planets in Reflected Light

Publications of the Astronomical Society of the Pacific, vol. 132, pp. 104502

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 (1.5–5.2 λ / 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.

Authors 5

1. Olivier Guyon

   University of Arizona · Astrobiology Center · National Astronomical Observatory of Japan

   Affiliation as printed

   Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588, Japan

   College of Optical Sciences, University of Arizona, Tucson, AZ 85721, USA

   Steward Observatory, University of Arizona, Tucson, AZ 85721, USA

   Subaru Telescope, National Astronomical Observatory of Japan, 650 North A‘ohōkū Place, Hilo, HI 96720, USA

2. Dan Sirbu

   Ames Research Center

   Affiliation as printed

   NASA-Ames Research Center, Moffett Blvd., Moffett Field, CA, USA; currie@naoj.org, thayne.m.currie@nasa.gov

3. R. A. Frazin

   University of Michigan

   Affiliation as printed

   Department of Climate and Space Sciences and Engineering, University of Michigan-Ann Arbor, MI 48109-2143, USA

4. B. Nemati

   California Institute of Technology · Jet Propulsion Laboratory

   Affiliation as printed

   Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91016, USA

5. Barnaby R. M. Norris

   The University of Sydney

   Affiliation as printed

   Sydney Institute for Astronomy, School of Physics, Physics Road, University of Sydney, NSW 2006, Australia