Surface plasmon resonances in a branched silver nanorod

Abstract

The properties of surface plasmon-polariton (SPP) resonance modes were investigated in a branched silver nanorod consisting of two nanorods using high energy resolution electron energy-loss spectroscopy (EELS) combined with scanning transmission electron microscopy. The experimental EELS maps of the SPP excitation showed a specific distribution depending on the resonance mode. The analytical formulas of the EELS signal and the resonance conditions for SPP resonance in the branched nanorod were derived by expanding the method reported for a one-dimensional straight resonator, and these were applied to interpret the experimental results. The SPP resonance in the branched nanorod can be attributed to Fabry-Perot type resonance that propagates in any of the three different resonance paths. It was also demonstrated that the modes of SPP resonance are changed by the position of the crossing point in the branched structure, which indicates that the combination of the lengths of the respective branches can be used to control the propagation path and the resonance energy of SPP waves in branched structures.