Pupil Plane Phase Apodization

Phase apodization coronagraphs are implemented in a pupil plane to create a dark hole in the science camera focal plane. They are successfully created as “Apodizing Phase Plates” (APPs) using classical optical manufacturing, and as “vector-APPs” using liquid-crystal patterning with essentially achromatic performance. This type of coronagraph currently delivers excellent broadband contrast ($\sim$10${}^{-5}$) at small angular separations (few $\lambda \mathrm{/}D$) at ground-based telescopes, owing to their insensitivity to tip/tilt errors.