Absorption-Mode Splitting of Terahertz Metamaterial Mediated by Coupling of Spoof Surface Plasmon Polariton

The resonant modes and their coupling effect of metamaterials is a rapidly growing research topic with potential for applications in optoelectronics. In this work, a strong absorption coupling between the spoof surface plasmon polariton (SSPP) modes and the intrinsic modes has been investigated in a novel terahertz metamaterial. The anticrossing effects of the absorption-mode coupling show a splitting frequency difference that can be described based on a Rabi-splitting-like model. The theoretical and experimental results demonstrate that the splitting phenomenon is induced by an energy exchange between the intrinsic mode and the SSPP mode. This coupling process is mediated by the SSPP mode and can be controlled efficiently by directionally varying the lattice constant of the metamaterial. Furthermore, this absorption process involving hybrid modes can lead to resonances with ultra-high quality factors, which will provide a strong platform for the applications in the field of sensing and detection.