Laboratory demonstration of high contrast with the PIAACMC coronagraph on an obstructed and segmented aperture

Abstract

Coronagraphs are an important technology to directly image and characterize exoplanets. Their efficiency has steadily been improving over the past several decades, but has not yet reached fundamental limits. In particular, the expected exoplanet yield for missions such as the Astro2020-recommended “IR/O/UV Flagship” can still be improved by factors of at least 2-3. One possible architecture that can enable at least a part of this improvement is the Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC). It features high throughput, small inner working angle (IWA), and almost no loss in PSF sharpness, and natively supports obstructed and segmented apertures. Historically, key disadvantages of PIAA have been poor tolerance to stellar angular sizes and maturity, but latest designs and demonstrations have made significant strides in this respect. We present the current status of our program to mature the PIAACMC technology. We first present our PIAACMC designs for LUVOIR-A and B, which resulted in improved expected yield of Exo-Earths relative to the baselines for both mission concepts. In particular, for LUVOIR-B, the yield improves from 28 to 42 due to improved tolerance to stellar angular size in our design. Our and vacuum demonstrations for the LUVOIR-A aperture at JPL’s High Contrast Imaging Testbed (HCIT) include: 1.9e-8 raw contrast in 10% broadband light between 3.5 and 8 l/D; 4.1e-8 and 1.6e-9 coherent contrasts in monochromatic light between 2-4 and 4-8 l/D, respectively. We also present measurements and analysis of sensitivity to tip/tilt jitter and stellar angular size and compare our test results to models.