Hybrid Lyot coronagraph for wide-field infrared survey telescope-astrophysics focused telescope assets: occulter fabrication and high contrast narrowband testbed demonstration

Hybrid Lyot coronagraph (HLC) is one of the two operating modes of the WFIRST-AFTA coronagraph instrument. It produces starlight suppression over the full 360-deg annular region and thus is particularly suitable to improve the discovery space around WFIRST-AFTA targets. Since being selected by the National Aeronautics and Space Administration in December 2013, the coronagraph technology is being matured to technology readiness level 5 by September 2016. We present the progress of HLC key component fabrication and testbed demonstrations with the WFIRST-AFTA pupil. For the first time, a circular HLC occulter mask consisting of metal and dielectric layers is fabricated and characterized. Wavefront control using two deformable mirrors is successfully demonstrated in a vacuum testbed with narrowband light ( 1-nm bandwidth at 516 nm) to obtain repeatable convergence below 8×10− 9 mean contrast in the 360-deg dark hole with a working angle between 3λ/ D and 9λ/ D with arbitrary polarization. We detail the hardware and software used in the testbed, the results, and the associated analysis.