Fig. 1. Schematic diagram of the designed dual-unctional metasurface. (a) Functional schematic diagram; (b) unit cell

Fig. 2. Response curves of different parameters to terahertz waves. (a) Elliptic long axis a; (b) short axis b; (c) dielectric layer thickness h; (d) metal strip width w

Fig. 3. Amplitude-phase characteristics of the unit cells under reflection mode. (a)(c) Amplitude; (b)(d) phase

Fig. 4. Phase arrangement of the proposed metasurface with different topological charges. (a) l=±1; (b) l=±2

Fig. 5. Results of left-handed circularly polarized waves incident on the metasurface in Fig. 4(a). (a)(e)(i)(m) Nar-field phase diagrams; (b)(f)(j)(n) electric field intensity diagrams; (c)(g)(k)(o) far-field radiation patterns; (d)(h)(l)(p) far-field phase diagrams

Fig. 6. Results of right-handed circularly polarized waves incident on the metasurface in Fig. 4(b). (a)(e)(i)(m) Phase diagram; (b)(f)(j)(n) electric field intensity diagram; (c)(g)(k)(o) far-field pattern; (d)(h)(l)(p) far-field phase diagram

Fig. 7. Mode purity of vortex beams generated by circular polarized waves incident on metasurfaces in Fig. 4 along -z direction. (a) l=+1; (b) l=+2; (c) l=-1; (d) l=-2

Fig. 8. Metasurface arrangement of quarter beam vortex beams with topological charge of l=-1. (a) Distribution of eight unit cells in vortex beam with topological charge of l=-1; (b) phase arrangement of the four beam divisions of the beam; (c) arrangement of eight unit cells for quarter beam vortex beam with topological charge of l=-1

Fig. 9. Far-field diagrams of beam splitting vortex with topological charge of l=-1. (a) Far-field radiation of xoy-plane; (b) 2D far-field diagram

Fig. 10. Metasurface arrangement of deflection vortex beams with topological charge of l=+2. (a) Metasurface elements distribution of vortex beam with topological charge of l=+2; (b) phase arrangement of deflection beam metasurface; (c) arrangement of eight unit cells for deflection vortex beam with topological charge of l=+2

Fig. 11. Far-field diagrams of deflection vortex with topological charge of l=+2. (a) 3D far-field radiation of xoz-plane; (b) 3D far-field radiation of xoy-plane; (c) 2D far-field diagram

Fig. 12. Phase distribution of superposition vortex beam metasurface. (a) Phase arrangement of deflection vortex beam with topological charge of l=-1;(b) phase arrangement of deflection vortex beam with topological charge of l=+2; (c) distribution of vortex beam with superimposed topological charges of l=-1 and l=+2

Fig. 13. Far-field of superposition vortex beam with topological charges of l=-1 and l=+2. (a) Far-field radiation of xoy-plane; (b) 2D far-field diagram

Fig. 14. Transmission amplitude and polarization conversion ratio of eight unit cells in transmission mode. (a) Transmission amplitude; (b) polarization conversion ratio

Fig. 15. Terahertz transmission amplitude phase curve in u-v axis under linearly polarized wave incidence at a frequency of 0.72 THz. (a) Transmission amplitude; (b) phase

Fig. 16. Surface current distribution under linearly polarized wave incident on metasurface along -z direction at 0.72 THz. (a) Left view of x-polarized wave incidence; (b) left view of y-polarized wave incidence; (c) top view of x-polarized wave incident; (d) bottom view of y-polarized wave incident

Fig. 17. Surface current distribution for linearly polarized wave incident on metasurface along +z direction at 0.72 THz. (a) Left view of y-polarized wave incident; (b) left view of x-polarized wave incident; (c) top view of x-polarized wave incident; (d) bottom view of y-polarized wave incident