Enhancing the performance of unidirectional excitation of surface-plasmon-polaritons in plasmonic couplers based on the nanoslit with bump

In this paper, we explore enhancing the performance of unidirectional excitation of surface-plasmon-polaritons (SPPs) in two plasmonic structures based on the nanoslit with bump. It is found that the introduction of dielectric layer in such two structures can greatly enhance the current density on metal–dielectric interface, the field confinement, the power flow carried by SPPs and the excitation efficiency of SPPs, owing to the SPP wavevector matching. The introduction of microcavity could further improve the current density and the power flow, since microcavity can collect more light in comparison with the case without microcavity. At optimized dielectric thickness and structural parameters of microcavity, the current density (power flow) could achieve over four (eleven) times that in the isolated slit–bump structure. We hope that our findings will provide more flexibility for designing ultracompact plasmonic coupler/generator and pave the way for using them in the practical application.