Fig. 1. Design strategies for transmissive reconfigurable metasurfaces composed of active and passive modules. (a) Both modules are narrowband. (b) Both modules are wideband. (c) The narrowband active module and the wideband passive module are strongly coupled. (d) The narrowband active module and the wideband passive module are weakly coupled. (e) The frequency shift in strongly coupled systems. (f) The frequency shift in weakly coupled systems.

Fig. 2. Preliminary design process of active and passive modules in transmissive reconfigurable metasurface. (a) Structure diagram of the active module. (b) Structure diagram of the passive module. (c) The simulated transmission coefficient under two working states of the active module. (d) The simulated transmission coefficient of the passive module at several different opening angles θ.

Fig. 3. (a) Scheme of the structure and working principle of the weakly coupled reconfigurable metasurface. The optimized parameters are as follows: P=6 mm, l1=4.3 mm, l2=3.5 mm, l3=0.95 mm, l4=3 mm, l5=2.6 mm, l6=6 mm, w1=0.2 mm, w2=2.5 mm, w3=0.5 mm, w4=1 mm, w5=0.5 mm, w6=1.5 mm, s1=0.3 mm, r1=2.8 mm, h1=1 mm, h2=2 mm, h3=2 mm. (b) The simulated transmittance under two working states at several different opening angles θ. (c) FDTD simulated PCR at the ON state. (d) FDTD simulated transmission phase response Φ with opening angles θ and frequency variation. (e) FDTD simulated PCR at the OFF state.

Fig. 4. Independent control of passive and active modules in transmissive reconfigurable metasurfaces based on weakly coupled units. (a) Illustrations of two cases: anomalous transmission and focal wavefront switching by weakly coupled reconfigurable metasurfaces. (b) Simulated normalized angular far-field distributions of the weakly coupled reconfigurable metasurface for anomalous transmission switching case at several working frequencies. Simulated 3D electric field intensity distribution of the weakly coupled reconfigurable metasurface for focal wavefront switching case under (c) OFF state and (d) ON state at 12 GHz.

Fig. 5. Experimental demonstration of the weakly coupled reconfigurable metasurface for focal wavefront switching. (a) Photograph of the weakly coupled reconfigurable metasurface sample (35×35 array). (b) Photograph of the near-field measurement setup for the reconfigurable screen in the anechoic chamber. (c) Scattered field intensity from FDTD simulation at OFF state. (d) Scattered field intensity from FDTD simulation at ON state. (e) Scattered field intensity from measurement at OFF state. (f) Scattered field intensity from measurement at ON state. (The simulation and experiment comparisons at the three operating frequencies were carried out in the yoz plane.) (g) Simulated and measured electric field intensity distribution at the focal point at different frequencies under the two working states of diodes.