SUPPPPRESS: developing low-leakage liquid-crystal vector vortex coronagraphs for space-based exoplanet imaging

We report on the ESA-funded SUPPPPRESS project, focused on developing high-performance liquid-crystal coronagraphs for the direct detection and spectral characterization of Earth-like exoplanets. The goal is to improve the contrast and operational spectral bandwidth of the Vector Vortex Coronagraph (VVC). We manufacture regular and multi-grating VVCs (mgVVCs), stacking two or three liquid-crystal masks (LCMs) with vortex and grating patterns to mitigate polarization leakage. This enables full exploitation of the VVC's achromatic and scale-invariant properties. We detail the improved manufacturing of LCMs by ColorLink Japan, Ltd. and their quality assessment using far-field diffraction, polarization microscopy, and zero-order leakage spectroscopy. The individual LCMs are assembled into mgVVCs using a custom jig. We demonstrate their broadband contrast performance on the THD2 testbed, comparing standard VVCs and mgVVCs. Finally, we discuss space environmental qualification of the masks.