Optically Reconfigurable Graphene/Metal Metasurface on Fe:LiNbO₃ for Adaptive THz Optics

We demonstrate, experimentally, nonvolatile optical control of terahertz metasurfaces composed of a metallic split-ring resonator array sandwiched between monolayer graphene and a photoconductive Fe:LiNbO3 substrate. We demonstrate frequency-selective tuning of THz transmission amplitude, and our results pave the way toward spatially resolved control of THZ metasurfaces for beam steering, imaging, and sensing applications. The substrate (Fe:LiNbO3) supports nonvolatile yet reversible photoinduced charge distributions, which locally modify the electrostatic environment of the nano-thickness graphene monolayer, altering the graphene electrical conductivity and therefore changing the resonance spectra of the metamaterial array. We present light-induced normalized transmittance changes up to 35% that are nonvolatile and persist after the illumination source is removed yet can be reversed by thermal annealing.