Probing the Near-Field Inductive Coupling in Broadside Coupled Terahertz Metamaterials

We discuss near-field coupling between the pair of split ring resonators (SRRs) in broadside coupled terahertz (THz) metamaterials and examine resonance split and tuning of resonances in such metamaterials system. The metamolecule design is comprised of two orthogonally twisted broadside coupled SRRs separated by a thin microscale polyimide layer. We analyze the interaction between the metalayers numerically and analytically by displacing the top resonator w.r.t. the bottom resonator both in the horizontal and vertical directions. The THz transmission through proposed configuration results in the split of fundamental resonances due to the resonance mode hybridization effect. In the case of successive horizontal displacements between the resonators, we observe a complete shift from the coupled to uncoupled state, however, in vertical displacements, we notice the transition from coupled to uncoupled state at much larger displacement. We employed a semianalytical transmission line model to understand and describe the coupling aspect between the bilayer resonators and found that it corroborates the numerical findings. The ability to tune resonance behavior that we have examined through this work, could be significant in the development of frequency tunable THz devices and build other promising applications such as THz modulators and antennas in the near future.