Abstract. The prospect of extreme high-contrast astronomical imaging from space has inspired developments of new coronagraph methods for exoplanet imaging and spectroscopy. However, the requisite imaging contrast, at levels of 1 billion to one or better for the direct imaging of cool mature exoplanets in reflected visible starlight, leads to challenging new requirements on the stability and control of the optical wavefront, at levels currently beyond the reach of ground-based telescopes. We review the design, performance, and science prospects for the hybrid Lyot coronagraph (HLC) on the WFIRST-AFTA telescope. Together with a pair of deformable mirrors for active wavefront control, the HLC creates a full 360-deg high-contrast dark field of view at 10 −9 contrast levels or better, extending to within angular separations of 3 λ 0 ∕D from the central star, over spectral bandwidths of 10% or more.

Predictions of contrast performance for the Eclipse coronagraphic telescope are based on computational models that are tested and validated with laboratory experience. We review recent laboratory work in the key technology areas for an actively-corrected space telescope designed for extremely high-contrast imaging of nearby planetary systems. These include apodized coronagraphic masks, precision deformable mirrors, and coronagraphic algorithms for wavefront sensing and correction, as integrated in the high contrast imaging testbed at JPL. Future work will focus on requirements for the Terrestrial Planet Finder coronagraph mission.

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We report our best laboratory contrast demonstrations achieved to date. We review the design, fabrication, performance, and future prospects of a hybrid focal plane occulter for exoplanet coronagraphy. Composed of thickness-profiled metallic and dielectric thin films vacuum deposited on a fused silica substrate, the hybrid occulter uses two superimposed thin films for control over both the real and imaginary parts of the complex attenuation pattern. Together with a deformable mirror for adjustment of wavefront phase, the hybrid Lyot coronagraph potentially exceeds billion-toone contrast over dark fields extending to within angular separations of 3 λ/D from the central star, over spectral bandwidths of 20% or more, and with throughput efficiencies up to 60%.We report laboratory contrasts of 3×10 -10 over 2% bandwidths, 6×10 -10 over 10% bandwidths, and 2×10 -9 over 20% bandwidths, achieved across high contrast fields extending from an inner working angle of 3 λ/D to a radius of 15 λ/D. Occulter performance is analyzed in light of recent experiments and optical models, and prospects for further improvements are summarized.The science capabilities of the hybrid Lyot coronagraph are compared with requirements of the ACCESS mission, a representative exoplanet space telescope concept study for the direct imaging and spectroscopy of exoplanet systems. This work has been supported by NASA's Technology Demonstration for Exoplanet Missions (TDEM) program.

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