Fig. 1
Schematic of the brickwork antenna tuneable capacitance modulator. a 3D view of the device area, the unit cell is indicated by a red dashed box; b an enlarged view of a metamaterial capacitor with the air gap in the graphene patch; and c a cross-sectional view of the device with the back-gate voltage source indicated. d Optical response of a “basic” L-C-R metamaterial structure: transmittance (black curve), reflectance of radiation incident from the air side (red curve) and from the substrate side (green curve). The curves are plotted using Eqs. (2)–(6) with dx = dy, n = 3.425, Γ/ω0 = 0.5, and γ/ω0 = 0.1. e, f Reflection from a metamaterial on a substrate with refractive index n: comparison between the excitation e from the top side and f from the back side. Vertical arrows show the direction of the electromagnetic wave vector; the horizontal arrows indicate the electric field direction. The coloured arrows indicate the direction of the reflected electric field from the substrate–air interface (blue) and from the metamaterial (orange)
