Demonstration of Coronagraph Technology for High-Contrast Point Spectroscopy of ExoEarths

The planned Habitable Worlds Observatory (HWO) will be designed to find and characterize Earth-like planets in the habitable zones of Sun-like stars. This mission will require an instrument capable of making measurements of planet spectra at high contrast and small inner working angles. Previous demonstrations of existing coronagraph designs have not achieved these requirements at the 20% bandwidths or better required for full spectroscopic characterization, even in a laboratory environment. One technique that shows promise for improving bandwidth is the allocation of deformable mirror (DM) degrees of freedom to improve bandwidth by relaxing requirements on the size of the coronagraph’s focal plane correction region, or dark zone (DZ). In this work, we provide details and results of a laboratory demonstration of a wide-band coronagraph in NASA’s High-Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory (JPL). We show that a D-shaped region on one half of the focal plane can be corrected to a contrast of 4×10−10 in a 20% bandwidth using a simple Lyot coronagraph with two DMs. We also provide details of future plans to improve contrast and bandwidth by further reducing the dark region to just the light coupled into a single-mode fiber in the coronagraph’s focal plane.