Fig. 1. Schematic illumination of the CBR-CM. The CBR-CM is constructed via symmetrically incorporating PIN diodes into an elaborately designed metasurface structure, and these diodes are controlled by multi-channel bias voltages provided by a FPGA-based control circuit connected to real-time holographic processing system. As illustrated examples, by arranging specific LCP and RCP 1-bit coding sequences, dynamic meta-holograms with identical focal length, variable focal length, switchable spatial pixels, and against arbitrary polarization state are successively demonstrated.

Fig. 2. Geometric configuration and EM responses of the dynamically reconfigurable meta-particle. (a) Perspective view of the proposed meta-particle. (b) Vertical and layered schematic of the proposed meta-particle. (c) The equivalent circuit models of the PIN diodes in the “ON” and “OFF” states. (d) Simulated surface current distributions on the proposed meta-particle of state “11/10” and “01/00” under LCP incidence at 10 GHz. (e) Simulated surface current distributions on the proposed meta-particle of state “11/01” and “10/00” under RCP incidence at 10 GHz. (f, g) Simulated co-polarized reflection amplitude and phase responses of the proposed meta-particle with coding states of “11”, “10”, “01”, and “00” under orthogonal CP normal incidence.

Fig. 3. Directional generation of meta-holograms with identical and variable focal length. (a) The target monochrome image of the letter “C” and corresponding phase coding patterns under the normal incidence of LCP waves. (b) The target monochrome image of the letter “D” and corresponding phase coding patterns under the normal incidence of RCP waves. (c) Numerically simulated and experimentally measured normalized electric field intensity of LCP component utilizing coding pattern in (a) in L_r-L_i channel on the x-y plane cutting at z=100 mm. (d) Numerically simulated and experimentally measured normalized electric field intensity of RCP component utilizing coding pattern in (b) in R_r-R_i channel on the x-y plane cutting at z=100 mm. (e) The target monochrome image of the letter “L” and corresponding phase coding patterns under the normal incidence of LCP waves. (f) The target monochrome image of the letter “R” and corresponding phase coding patterns under the normal incidence of RCP waves. (g) Numerically simulated and experimentally measured normalized electric field intensity of LCP component utilizing coding pattern in (e) in L_r-L_i channel on the x-y plane cutting at z=100 mm. (h) Numerically simulated and experimentally measured normalized electric field intensity of RCP component utilizing coding pattern in (f) in R_r-R_i channel on the x-y plane cutting at z=150 mm. All of the results are simulated and measured at frequency of 10 GHz.

Fig. 4. Multifunctional customization of meta-holograms with switchable spatial pixels. (a) The target monochrome image of the letter “S” and scanning trajectory of LCP and RCP spatial pixels under the normal incidence of orthogonal CP waves. (b) Four groups of sequentially and synchronously switched spatial pixels (σ_-,1, σ_+,1), (σ_-,2, σ_+,2), (σ_-,3, σ_+,3) and (σ_-,4, σ_+,4) distributions in L_r-L_i and R_r-R_i channels, respectively. The subscript “-” and “+” represent the LCP and RCP reflection channels. (c–f) The target monochrome image and phase coding patterns of spatial pixel σ_-,1, σ_-,2, σ_-,3, and σ_-,4. (g–j) The corresponding simulated and measured normalized electric field intensity of LCP component on the x-y plane cutting at z=100 mm. (k–n) The target monochrome image and phase coding patterns of spatial pixel σ_+,1, σ_+,2, σ_+,3, and σ_+,4. (o–r) The corresponding simulated and measured normalized electric field intensity of RCP component on the x–y plane cutting at z=100 mm. All of the results are simulated and measured at frequency of 10 GHz.

Fig. 5. Cyclic evolution of meta-holograms against arbitrary polarization states on Poincaré sphere. (a) The target monochrome image of the symbol “+” and corresponding phase coding patterns of LCP basis vector and RCP basis vector. (b) Schematic of eight typical SOPs on Poincaré sphere. The numerically simulated and experimentally measured amplitude and phase profiles of normalized electric field of LCP and RCP components under the normal incidence of (c) LP-0° (linear polarized vibrating along 0° angle with respect to horizontal axis), (d) LP-90°, (e) LP-45°, (f) LP-135°, (g) LCP, (h) RCP waves, (i) ELCP (elliptical left-handed circularly polarized), and (j) ERCP (elliptical right-handed circularly polarized) waves. All of the results are simulated and measured at frequency of 10 GHz.

Table 1. Eight characteristic polarization states with their corresponding orthogonal CP states decomposition.