Fig. 1. Schematic of coupling meta-atom and its realistic light deflection of WCAFR. All lights which have impact on the metasurface will deflect and intersect at the focal point. In the transverse dimension, the surface current distribution shows the order of the plasmonic mode on the meta-atom pattern. In the longitudinal dimension, there is a sketch map of diffraction mechanism and multiple reflections effect for reflective Fabry–Perot resonators. Every single unit can be regarded as an F-P resonator, inside which the wave oscillates back and forth i times and is reflected as the ith order output wave. (P.A., power amplitude.) The coupling between the transverse plasmonic mode and longitudinal F-P resonant mode enlarges the efficiency of LCMs, and further promotes the permittivity level. (i.p., ideal permittivity; the simulation results are obtained based on Appendix A. All dielectric material considered in derivations is F4B: ε=2.65+0.001i.)

Fig. 2. (a) Normal standing wave performance formed on the boundary between two media. (b) Ideal operating bandwidth of the reflective meta-atom [A=0.9 means the consideration of most incident electromagnetic power (81%)]. The results are obtained based on Eq. (3). Here the common F4B is considered as the model dielectric material and its parameter is ε=2.65+0.001i.

Fig. 3. (a) and (d) The normalized electric susceptibility of dipole under liner-polarization incidence and S-pattern under circular-polarization incidence (χe=χ′−iχ′′, ε∝χe). (b) and (e) The performances of two meta-atoms with different operating bandwidths. Here the dipole is regarded as the transmissive type, so the transmission curve tyy is the work band. The blue covered regions in (a) to (d) are the anomalous dispersive band. (c) and (f) show the different plasmonic modes on the meta-atoms.

Fig. 4. Performances of WCAFR. (a) Focal lengths and shifts of diffraction limits and WCAFR under different illuminated frequencies. (b) The calculated intensity distribution of diffraction limits in the xoy plane. (c), (d) Simulated and measured intensity distributions of WCAFR in the xoy interceptive plane. The incident wave frequencies are denoted on the top left corner. The incident direction is along the positive z axis. (e) Normalized intensity profiles along the green dashed lines of (c). The green dashed lines pass through the center of focal spots in the case of frequency  18.0  GHz. The white dashed frame parts are considered as the focal spot.

Fig. 5. Efficiencies of five observed frequency points.

Fig. 6. Relations among the cavity thickness (d), frequency, and absorption coefficient show the periodicity of SWM and it also provides an optimal solution to the cavity thickness d=2  mm.

Fig. 7. (a) The phase for a WCAFR at arbitrary frequency of freq.∈(fmin,fmax). (b) The achromatic phase mechanism scheme in our work. (The x coordinate is not 0 at the point where the y axis intersects the x axis.) (c) The nonlinear relation between the proportional coefficient and meta-atom position. (d) The phase distribution of the meta-atom.

Fig. 8. Circular incidence scheme for dipole with the α rotation angle.

Fig. 9. Near-field demonstration for the WCAFR metasurface. (a) Schematic of near-field measuring for the proposed WCAFR metasurface. (b) The surroundings and relevant details for the measuring experiment.