Development of segmented photonic-crystal phase masks for spectral characterization of exoplanets

We are developing coronagraphic segmented phase masks designed for the direct detection and spectral characterization of Earth-like exoplanets. We expect that the segmented phase masks can achieve relatively high core throughput and a small inner working angle (IWA). We have performed numerical simulations to evaluate the core throughput and IWA for segmented phase masks of various orders. Additionally, we simulated observed images for target stars at different distances and spectral types, assuming Earth-like planets in their habitable zones. Development of the phase masks is also underway. We are iteratively designing and prototyping broadband phase masks using three-layer photonic crystals optimized for the visible and near-infrared regimes, and the fabricated masks are evaluated in the laboratory. In this presentation, we will report on the recent activities of our ongoing simulations and mask development efforts.