Fig. 4From: Dielectric metasurface zone plate for the generation of focusing vortex beamsThe measured intensity profiles at the focal planes of the metasurface device with topological charge of l = 2 at wavelength of 633 nm. a H-H polarization configuration. b H-V polarization configuration. c The measured optical efficiencies of the metasurface devices with topological charges of l = 2 (red lines) and l = 3 (blue lines). ‘H-H’, ‘H-V’ represent the horizontally polarized incident light with a horizontally or vertically polarized analyzer for the transmitted waveBack to article page