Fig. 1. Schematics diagram of the metasurface unit cell structure. (a) 3D structural; (b) top view

Fig. 2. Equivalent hypersurface units and corresponding coding elements in different states. (a) State A; (b) state B; (c) state C

Fig. 3. Reflection amplitude and reflection phase of metasurface unit cells corresponding to different states when LCP is normally incident. (a)(b) State A; (c)(d) state B; (e)(f) state C

Fig. 4. 2-bit coding elements in state A with ∇φ1=π/2/P phase gradient. (a) 00; (b) 01; (c) 10; (d) 11

Fig. 5. 2-bit coding elements in state B with ∇φ2=π/3/P phase gradient. (a) 00; (b) 01; (c) 10; (d) 11

Fig. 6. 2-bit coding elements in state C with ∇φ3=2π/9/P phase gradient. (a) 00; (b) 01; (c) 10; (d) 11

Fig. 7. Far-field scattering and angle when the LP wave at 1.2 THz is incident vertically. (a) Far-field scattering of the coding phase gradient metasurface; (b) azimuth φ and pitch θ of the four vortex beams

Fig. 8. Far-field scattering and angle when the LP wave at 1.0 THz is incident vertically. (a) Far-field scattering of the coding phase gradient metasurface; (b) azimuth φ and pitch θ of the four vortex beams

Fig. 9. Far-field scattering and angle when the LP wave at 0.54 THz is incident vertically. (a) Far-field scattering of the coding phase gradient metasurface; (b) azimuth φ and pitch θ of the four vortex beams