(a) Schematic view of the unit cell of the Fano resonant metasurface, which consists of an array of THz asymmetric spit-ring resonators. Measured [(b)–(e)] and simulated [(f)–(i)] transmission spectra of metasurface with different values of d before (orange lines) and after (blue lines) the graphene deposition. The polarization of the incident THz electric field is vertical to the gaps. Figure reprinted with permission: Ref. [53], ©2016 by the Royal Society of Chemistry.