Fig. 1. (a) Schematic diagram of the proposed reflective-mode metallic metasurface structure. (b) Schematic diagram of the single unit structure of the metasurface with structural parameters. (c) Schematic diagram of the principle of detour phase.

Fig. 2. Effect of ring width and groove depth on (a) the polarization ER and (b) the efficiency of the metasurface. Far-field distribution of the reflected light when the incident light is (c) LCP and (d) RCP with the optimized parameters. (e) Comparison of −1st, 0th, +1st diffraction order far-field intensity between LCP and RCP incidence. (f) The efficiency and ER as a function of incident wavelength.

Fig. 3. Far-field distribution of the generated OV beam in the case of (a) RCP (l = −1), (b) LCP (l = +1), and (c) LCP (l = +2). The insets on the top-right corner, lower-left corner, and lower-right corner show the enlarged distribution of intensity, phase distribution on metasurface, and phase of the OV beam, respectively. (d) Phase distribution diagram of vortex Damman grating for 3 × 3 OV array. (e) 3 × 3 OV array with topological charges ranging from −4 to +4 is generated under LCP illumination. The modulated 3 × 3 OV array when the incident light is an OV beam with topological charge (f) l₀ = −1 and (g) l₀ = +2.

Fig. 4. (a) Schematic diagram of the experimental system. (b) SEM image of the metasurface sample. Comparison of experimental results of left-/right-side reflected pattern under LCP/RCP incidence with (c) the uniform grating structure of semicircular nano-grooves and (d) the metasurface structure to generate OV beams with topological charge l = 1.