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The apodizing phase plate (APP) is a solid-state pupil optic that clears outa D-shaped area next to the core of the ensuing PSF. To make the APP moreefficient for high-contrast imaging, its bandwidth should be as large aspossible, and the location of the D-shaped area should be easily swapped to theother side of the PSF. We present the design of a broadband APP that yields twoPSFs that have the opposite sides cleared out. Both properties are enabled by ahalf-wave liquid crystal layer, for which the local fast axis orientation overthe pupil is forced to follow the required phase structure. For each of the twocircular polarization states, the required phase apodization is thus obtained,and, moreover, the PSFs after a quarter-wave plate and a polarizingbeam-splitter are complementary due to the antisymmetric nature of the phaseapodization. The device can be achromatized in the same way as half-wave platesof the Pancharatnam type or by layering self-aligning twisted liquid crystalsto form a monolithic film called a multi-twist retarder. As the VAPP introducesa known phase diversity between the two PSFs, they may be used directly forwavefront sensing. By applying an additional quarter-wave plate in front, thedevice also acts as a regular polarizing beam-splitter, which thereforefurnishes high-contrast polarimetric imaging. If the PSF core is not saturated,the polarimetric dual-beam correction can also be applied to polarizedcircumstellar structure. The prototype results show the viability of thevector-APP concept.

The Vector-APP: a Broadband Apodizing Phase Plate that yields Complementary PSFs