Fig. 1. Schematic of the proposed metasurface for polarization modulations in transmission mode. By controlling the states of the SPDT switches, the metasurface with double-sided metallic patterns can realize four linearly polarized states (X-to-X, X-to-Y, Y-to-X, and Y-to-Y) and perfect reflection.

Fig. 2. Exposition of the multilayer element with specific parameters. (a) Profile of the adopted element and the states of the SPDT switches. (b) Top view and (c) bottom view of the element. (d) 3D view of the element structure.

Fig. 3. (a) Designed modulation situation and digital coding patterns. (b)–(e) Simulated amplitudes of the transmission coefficients for elements in the states of (b) 00, (c) 01, (d) 10, and (e) 11, corresponding to patterns A, B, C, and D.

Fig. 4. Combined coding patterns and related simulation results. (a)–(d) Representative combined coding patterns (E, F, G, and H) with multifunctionalities expressed as 00010001, 10111011, 00110011, and 00010001/10111011, as well as the transmission power illustrations. (e)–(h) Related simulation results of transmission coefficients, in which the data of all four channels are included (X–X, X–Y, Y–X, and Y–Y).

Fig. 5. Experimental setup of the proposed programmable metasurface. (a) Photograph of the fabricated sample. (b) Schematic of the experimental setup. (c)–(f) Measured transmission coefficients S21 of: (c) pattern A; (d) pattern B; (e) pattern E; and (f) pattern F.

Fig. 6. Design and simulations of near-field information transmission using binary ASCII codes. (a) Schematic of the binary information representation and transmission. (b)–(l) Simulated near-field electric field distributions of three groups of letters in binary ASCII codes: HI, SUEP, and SEU.

Fig. 7. Experimental demonstrations of the near-field information transmissions using binary ASCII codes. (a), (b) Configuration of near-field measurements. (c)–(h) Measured results of six letters represented with binary ASCII codes: (c) H, (d) I, (e) S, (f) U, (g) E, and (h) P.