A functional metasurface of both transparent medium slices and multiple deflection prisms is proposed, where phase retardations for generating non-diffracting vortex lattices are integrated and encoded as rotation angles of nano-apertures. Under plane-wave illumination, the transmitted waves from the thin flat metasurface act analogously as multiple beams, each with a designed propagating direction and pre-scribed phase shift, that generate an optical lattice within their overlapping region of space. By altering the design parameters of the metasurface, lattice type and size can be controlled. Both numerical simulations and experiments were conducted, verifying the possibility of the proposed method and the non-diffracting properties of the generated vortex lattices.
In this paper, we generated polarization-independent ring-Airy beams by designing metasurfaces that can realize modulations of both phase and amplitude. In numerical simulation, such metasurfaces are designed by placing subwavelength rectangular slits in Au film uniformly. Two orthogonal types of slits, with orientation angles of 45 and −45 degrees, are used to obtain the binary phase profile in the light transmitted from the metasurface under illumination with either right circular polarization (RCP) or left circular polarization (LCP). This satisfies the phase required for Airy beam generation. Meanwhile, the difference between the phase profile under RCP illumination and that under LCP illumination is right 2π, which can be regarded as the same. This makes the metasurface available to generate Airy beams regardless of incident polarization. We also analyzed the auto-focusing, self-healing, and frequency-response properties of the generated Airy beams with different parameters. This work opens up more opportunities for applications of Airy beams.
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