Transmission characteristics of surface plasmon polaritons in -shaped resonator

Abstract

To improve the efficiency of transmission, in this paper, we propose a structure of the surface plasmon polariton embedded in a sliver circular resonator with a sliver nanoellispod(-shaped resonator), and also investigate its optical properties by the finite element method. Firstly, we study the optical properties of -shaped resonator at a=120 nm and =0 with different values of b. The results show that the -shaped resonator structure has the narrow transmission peaks, and the transmittance spectrum can be tuned by modifying the structure parameters. So this nanostructure would find applications in the designing of the novel filter. Secondly, compared with the former Fano resonance which results from the localized plasmon resonance coupling, the Fano resonance which results from the resonance of the surface plasmon polaritons coupling is represented by this structure. When the symmetry of -shaped resonator is broken, the Fano resonance will be observed clearly. Like the Fano resonance which results from the localized plasmon resonance coupling between the bright mode of metallic nanostructure and the dark mode of metallic nanostructure, the results show that the dipolar, quadrupolar, and octupolar Fano resonances of -shaped resonator structure occur, which are caused by the destructive interference between the bright dipolar mode and the dark dipolar mode, quadrupolar mode, and octupolar mode. When we take the rotation angle as 0 and 90, 15 and 75, 30 and 90 respectively, the Fano asymmetric transmittance spectra of -shaped resonator are similar, which result from the same degree of asymmetry. The larger the degree of asymmetry of the -shaped resonator structure, the more obvious the Fano resonance is. Thirdly, the size of this structure has significant effects on the transmission peak positions, line width, and intensity of the Fano resonance, in particular, in the case that =0 corresponds to the generation of FR(FR on) and in the case corresponding to the vanishing of FR(FR off). therefore, this phenomenon of -shaped resonator will provide a new strategy for the surface plasmon polariton Fano switch. We hope that this nanostructure has potential applications in designing filter, biological sensors, and Fano switch.