AstroPIC: Near-Infrared photonic integrated circuit coronagraph architecture for the Habitable Worlds Observatory

The Habitable Worlds Observatory (HWO) is the leading recommendation of the Astro2020 decadal survey. The HWO flagship, to be launched in the early 2040s, will directly survey 100 of the nearest stellar systems and their habitable zones with the goal of detecting and spectroscopically characterizing 25 potentially “Earth-like planets” (or “Exo-Earths”). Photonic-based technologies can substantially improve technical and science margins by improving coronagraphic efficiency for HWO. We present the architecture of a photonic-integrated circuit (PIC)-based coronagraph (“AstroPIC”), currently being studied as a near-infrared channel coronagraph that can be adopted as part of a suite of coronagraphs that could be deployed on the HWO. The PIC architecture miniaturizes a traditional coronagraph reducing the mass and volume of the coronagraph while providing an avenue to simply enhance the functionality, bandwidth coverage, and exoplanet yield of HWO by adopting a Mach-Zehnder Interferometric (MZI) mesh for photonic nulling. In this architecture we consider two cases: (1) a hybrid AstroPIC using a small number of modes (16-25) can still enhance exoplanet yields through complementary coronagraphic sensitivities to a traditional coronagraph, and (2) a full photonic chip AstroPIC that uses larger number of modes (400+) that can be operated as a stand-alone coronagraph that approaches the optimal coronagraph performance limit. We summarize recent experiments carried out at the Stanford photonic teststand which demonstrate key coronagraphic functionality including: (1) 1e-7 contrast (70 dB nulling) achieved with a simple PIC consisting of a 4-MZI mesh, (2) 8e-9 contrast (81 dB nulling) achieved with 6-MZI elements, and (3) a free-space coupling on chip of a beam demonstrating coronagraphic nulling and coronagraphic throughput of an off-axis source. We discuss the recent AstroPIC Cycle-1 tape-out which will enable additional coronagraphic demonstrations including deeper nulling and scaling to larger numbers of modes initiating a technology development process to mature PIC-based coronagraphy for inclusion into HWO.