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

TL;DR

This paper demonstrates laboratory tests of Spatial Linear Dark Field Control (LDFC) that effectively maintain deep contrast in high-contrast imaging systems, advancing the capability to image exoplanets around stars.

Contribution

First laboratory demonstration of Spatial Linear Dark Field Control (LDFC) achieving contrast levels suitable for exoplanet imaging with space and ground telescopes.

Findings

LDFC restores and maintains dark holes with minimal contrast degradation.

LDFC requires fewer iterations and commands compared to classical speckle nulling.

Results suggest LDFC can improve high-contrast imaging efficiency and stability.

Abstract

Imaging planets in reflected light, a key focus of future NASA missions and ELTs, requires advanced wavefront control to maintain a deep, temporally correlated null of stellar halo -- i.e. a dark hole -- 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 ($\sim$ 5$\times$10$^{-7}$) and separations (1.5--5.2 $\lambda$/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 30m 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 dark hole 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 DM commands to reach contrasts obtained by spatial LDFC. Our results provide a promising path forward to maintaining dark holes 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.