Exoplanet Explorer: polarization aberrations in nulling interferometry

One of the objectives of modern astronomy is the characterization of terrestrial exoplanets orbiting Sun-like stars in the mid-infrared, where instruments face requirements that can only be overcome by nulling interferometry. Particularly, optical effects such as polarization aberrations require careful attention for they deteriorate the null depth. Using the optical design of the Exoplanet Explorer concept study, we simulate the influence of polarization aberrations over the 3–20 μm band, analyze their impact on the null depth and propose multiple compensation strategies for polarization aberrations. Furthermore, we present our nulling interferometry test bench, where we will experimentally investigate polarization aberrations in the beam combiner and phase shifter to provide more insights into the required polarization errors. These results will be used to implement polarization control subsystems in our 4-beams broadband nulling interferometry test bench CAPIBARA (Combining 4 APertures for mid-Infrared Broadband Analysis of Rocky-exoplanets Atmospheres).