Encrypting information through controlling polarization distributions in far field

Thanks to the precise control of the amplitude, phase and polarization at the subwavelength scale, metasurfaces have attracted tremendous attention on achieving multifunctional applications, such as metalens[1], meta-holograms [2], vortex generators [3] and so on. In order to multiplex multiple information in a single metasurface, various channels of metaholograms have been explored, including color channel in near or far field, amplitude channel, polarization channel, and position channel [4-8]. However, the polarization channel in far field has not been deeply investigated. Due to the ignored phase of reconstructed holograms in far field, the polarization at the overlapping area of different meta-holograms is generally distributed randomly. Actually, the phase difference plays an important role in determining the vectorial distribution. Up to now, only a few work has explore the importance of controlling the phase difference in far field [9-11]. Here, we study the relationship between the phase distributions in both near and far field and proposed a flexible strategy to multiplexing holographic images with a dielectric metasurface that can encode vectorial holographic images in far field via the controllability of phase difference of two arbitrary holographic images designed for the right circular polarized (RCP) light and left circular polarized (LCP) light on the imaging plane.