  Directly imaging Earth-sized exoplanets with a visible-light coronagraph
instrument on a space telescope will require a system that can achieve
$\sim10^{-10}$ raw contrast and maintain it for the duration of observations
(on the order of hours or more). We are designing, manufacturing, and testing
Dual Purpose Lyot coronagraph (DPLC) masks that allow for simultaneous
wavefront sensing and control using out-of-band light to maintain high contrast
in the science focal plane. Our initial design uses a tiered metallic focal
plane occulter to suppress starlight in the transmitted coronagraph channel and
a dichroic-coated substrate to reflect out-of-band light to a wavefront sensing
camera. The occulter design introduces a phase shift such that the reflected
channel is a Zernike wavefront sensor. The dichroic coating allows higher-order
wavefront errors to be detected which is especially critical for compensating
for residual drifts from an actively-controlled segmented primary mirror. A
second-generation design concept includes a metasurface to create
polarization-dependent phase shifts in the reflected beam, which has several
advantages including an extended dynamic range. We will present the focal plane
mask designs, characterization, and initial testing at NASA's High Contrast
Imaging Testbed (HCIT) facility.
