Multimode hybridizations in surface plasmon resonances excited in terahertz dipole cavities

Abstract

Inventive design variations in subwavelength plasmonic structures can excite unconventional surface plasmon resonances (SPRs) that can enormously contribute to developing futuristic terahertz (THz) devices and components. Therefore, in this work, we demonstrate multimode resonance features in SPR characteristics through the introduction of split-ring resonators (SRRs) in plasmonic dipole cavities operating in the THz domain. Here, we propose a hybrid plasmonic system, where a single SRR is placed in the middle of a dipole cavity sustaining SPRs in the THz domain. Further, the SRR is displaced in orthogonal directions (horizontally as well as vertically) from the center of the cavity introducing asymmetry in the hybrid SRR–dipole cavity system. In such a way, introduced asymmetry resulted in diverse transmission responses with the realization of multiple SPR peaks. Such multi-SPR features are explicated using two-state and three-state mode hybridization schemes, which arise due to the near-field electric coupling between the SRR and the dipole cavity. Our findings based on multimode SPR characteristics excited in planar dipole cavities can contribute to realizing compact biosensor, absorber, and nonlinear THz devices operating simultaneously in multiple frequency bands.