Simultaneous field enhancement and loss inhibition based on surface plasmon polariton mode hybridization

In common plasmonic configurations, energy loss and field enhancement are mutually restricted. In a vast majority of cases, high confinement goes together with high loss, which is a serious limitation for some applications. In an attempt of breaking this rule, which holds true for surface plasmon polariton (SPP) resonators, a multilayer trench grating microstructure with an asymmetric waveguide is considered. It supports both Fabry-Perot (FP) and cavity modes, whose hybridization exhibits unusual properties. The electric field enhancement was modulated by regulating the corresponding absorption and radiation quality factors. At the same time, energy loss was reduced, which is fundamentally ascribed to the mutual recycling of radiation energy between FP and cavity resonators. The maximum total quality factor and strongest field enhancement were both observed at the vicinity of quasi-static limit, thereby signifying that the structure exhibited simultaneous optimizations of field enhancement and loss inhibition, which is crucial to the design of high-quality SPP-based devices.