Fig. 1. Experimental setup of “parallel-plate waveguide-metasurface” system. (a) Diagram of “parallel-plate waveguide-metasurface” system; (b) microscopy image of typical metasurface used in this study (scale bar: 200 μm); (c) structural diagram of split ring pair corresponding to Fig. 1(b)

Fig. 2. Microscopy images of a series of metasurfaces fabricated in experiment.(a)--(e) Movement of gap in split ring 2 along x axis; (f)--(j) movement of gap in split ring 2 along z axis

Fig. 3. Transmission spectra when the gap in split ring 2 is moved along the x axis. (a) Experimental results (the inset in each subfigure is the corresponding metasurface arrangement); (b) simulated results (the insets display the surface current distributions at the resonance frequencies); (c) theoretically fitted results

Fig. 4. Electric field absolute distributions at transmission window frequencies corresponding to Fig. 3(b). (a) δx=-25 μm; (b) δx=-12.5 μm; (c) δx=0 μm; (d) δx=12.5 μm; (e) δx=25 μm

Fig. 5. Transmission spectra when the gap in split ring 2 is moved along the z axis. (a) Experimental results (the inset in each subfigure is the corresponding metasurface arrangement); (b) simulated results (the insets display the surface current distributions at the resonance frequencies); (c) theoretically fitted results

Fig. 6. Electric field absolute distributions at transmission window frequencies corresponding to Fig. 5(b).(a) δz=-25 μm; (b) δz=-12.5 μm; (c) δz=0 μm; (d) δz=12.5 μm; (e) δz=25 μm