Fig. 1. (a) Schematic of the full-space trifunctional metasurface; (b), (c) perspective and side view of the meta-atom; (d), (e) top layer and bottom layer of the meta-atom. The dielectric substrate is polyimide (lossy) with a permittivity of 3.5 and a loss tangent of 0.0027, and the metallic part is copper with a conductivity of σ = 5.8 × 10⁷ S/m. The metallic layer of each meta-atom can be divided into inner and outer parts; the outer part consists of a reversed SRR structure, and the inner part consists of a complementary ellipse structure. The geometric parameters of the meta-atom are as follows: p = 100 µm, t_s = 25 µm, t_m = 5 µm, r_v = 22 µm, r_u = 10 µm, r₁ = 43 µm, r₂ = 30 µm, w = 5 µm, s = 16 µm.

Fig. 2. Electromagnetic response of different meta-atoms. (a), (b) Reflection amplitudes and reflection phase under (a) LP and (b) CP waves at the frequency of 1.67 THz; (c) surface current distributions at the top and bottom copper layers under the LCP excitation at the frequency of 1.67 THz; (d), (e) transmission amplitudes and transmission phase under (d) LP and (e) CP waves at the frequency of 0.51 THz; (f) surface current distributions at the top and bottom copper layers under the LCP excitation at the frequency of 0.51 THz.

Fig. 3. (a) Reflection amplitudes, phases, and phase difference of the seven meta-atoms comprising the subarray under LP waves at the frequency of 1.67 THz; (b) transmission amplitudes, phases, and phase difference of the seven meta-atoms comprising the subarray under LP waves at the frequency of 0.51 THz.

Fig. 4. (a)–(c) Under the LCP excitation at the frequency of 1.67 THz, the resonant, geometric, and total phase distributions of the meta-atoms for the reflected Bessel beam; (d)–(f) under the RCP excitation at the frequency of 1.67 THz, the resonant, geometric, and total phase distributions of the meta-atoms for the reflected beam deflection; (g)–(i) under the LCP excitation at the frequency of 0.51 THz, the resonant, geometric, and total phase distributions for the meta-atoms of the transmitted beam focusing.

Fig. 5. Reflected Bessel beam generation under the LCP excitation at the frequency of 1.67 THz. (a) Schematic diagram of the Bessel beam generation under the LCP excitation; (b) electric field E_y distribution on the xoz plane under the LCP excitation; (c) intensity distribution on the xoz plane under the LCP excitation; (d) normalized intensity profile along a horizontal cut at z = 1900 µm.

Fig. 6. Reflected beam deflection under the RCP excitation at the frequency of 1.67 THz. (a) Schematic diagram of the beam deflection under the RCP excitation; (b) electric field E_y distribution on the xoz plane under the RCP excitation; (c) far-field polar plot under the RCP excitation at 1.67 THz; (d) far-field intensity distribution as a function of the frequency and polar angle under the RCP excitation; the red color column is simulated, while the blue color star is theoretical, representing the simulated and theoretically predicted deflection angles, respectively.

Fig. 7. Transmitted beam focusing under the LCP excitation at the frequency of 0.51 THz. (a) Schematic of the focusing lens at 0.51 THz; (b) electric field E_y distribution on xoz plane under the LCP excitation; (c) intensity distribution on the xoz plane under the LCP excitation; (d) normalized intensity profile along a horizontal cut at z = −800 µm.