文摘
We propose the design of a planar dielectric metasurface to overcome the ohmic loss and discrete phase profile of metallic metasurfaces. The proposed metasurface is composed of annular subwavelength gratings, which can be taken regard as a space-variant Pancharatnam–Berry phase optical element. Consequently, the OAM-carrying beams with topological charge ℓ = ±2 is generated with the efficiency high up to 90 %. In addition, we demonstrate a method to produce fractional, quasi-focusing, and quasi-non-diffracting OAM-carrying beams by adopting appropriate width modulation of the annular gratings. The proposed metasurfaces offering superiorities in high efficiency, phase continuity, and manipulative diversity may have potential applications in integrated-photonics and optical communication system. Keywords Metamaterials Optical vortices Subwavelength structures Nanostructures