Phase-Induced Amplitude Apodization (PIAA) coronagraphy: Recent results and future prospects

The Phase Induced Amplitude Apodization (PIAA) concept uses aspheric optics to apodize a telescope beam for high contrast imaging. The lossless apodization, achieved through geometrical redistribution of the light (beam shaping) allows designs of high performance coronagraphs, ideally suited for direct imaging of exoplanets similar to Earth around nearby stars. The PIAA coronagraph concept has evolved since its original formulation to mitigate manufacturing challenges and improve performance. Our group is currently aiming at demonstrating PIAA coronagraphy in the laboratory to 1e-9 raw contrast at 2 λ/D separation. Recent results from the High Contrast Imaging Testbed (HCIT) at NASA JPL and the PIAA testbed at NASA Ames demonstrate contrasts about one order of magnitude from this goal at 2 λ/D. In parallel with our high contrast demonstration at 2λ/D, we are developing and testing new designs at a complementary testbed at NASA Ames, and solving associated technical challenges. Some of these new PIAA designs have been tested that can further mitigate PIAA manufacturing challenges while providing theoretically total starlight extinction and offering 50% throughput at less than 1 λ/D. Recent tests demonstrated on the order of 1e-6 contrast close to 1 λ/D (while maintaining 5e-8 contrast at 2 λ/D).