A Single Noninterleaved Metasurface for High-Capacity and Flexible Mode Multiplexing of Higher-Order Poincaré Sphere Beams.

Cylindrical vector vortex beams, a particular class of higher-order Poincaré sphere beams, are generalized forms of waves carrying orbital angular momentum with inhomogeneous states-of-polarization on their wavefronts. Conventional methods as well as the more recently proposed segmented/interleaved shared-aperture metasurfaces for vortex beam generation are either severely limited by bulky optical setups or by restricted channel capacity with low efficiency and mode number. Here, a noninterleaved vortex multiplexing approach is proposed, which utilizes superimposed scattered waves with opposite spin states emanating from all meta-atoms in a coherent manner, counter-intuitively enabling ultrahigh-capacity, high-efficiency, and flexible generation of massive vortex beams with structured state-of-polarization. A series of exemplary prototypes, implemented by sub-wavelength-thick metasurfaces, are demonstrated experimentally, achieving kaleidoscopic vector vortex beams. This methodology holds great promise for structured wavefront shaping, vortex generation, and high information-capacity planar photonics, which may have a profound impact on transformative technological advances in fields including spin-Hall photonics, optical holography, compressive imaging, electromagnetic communication, and so on.