Tunable broadband multiresonance graphene terahertz sensor

We proposed a tunable multiresonance graphene sensor consisting of a graphene disk and three non-overlapping graphene rings on a dielectric substrate. Compared to the previous reports, our proposed graphene sensor acts in an ultrawide spectral range from mid-to far-infrared ranges. The resonance of the graphene disk is in the mid-infrared range, while the resonance of graphene rings is in the far-infrared range. The multiple plasmonic resonance of the proposed structure is highly sensitive to the change of the substrate permittivity such that the frequency sensitivity of the graphene disk, ring 1, ring 2, and ring 3 are 2.72, 0.878, 0.582, and 0.529 THz (THz) per substrate permittivity unit (THz/SPU), respectively. Interestingly, by increasing the radii of each graphene subarray ring a red-shift of the transmission resonance dips toward the THz frequencies can be observed. It is found that by changing the Fermi energy of graphene, each resonance dip of the proposed structure can be flexibly controlled without re-manufacturing the structure. The performance of our proposed structure makes it a powerful tool for using in the optical devices with operating in the mid-to far-infrared range.