Multiple out-of-plane plasmonic resonances in thick metallic rod with a cavity

We propose a nanostructure composed of a thick metallic rod with a cavity, in which multiple out-of-plane plasmonic resonances can be excited. When the cavity is laterally shifted to form an asymmetric nanostructure, the coupling between the plasmonic resonances excited in an individual element of the rod produces high-order hybridized out-of-plane modes with narrow linewidth. A further analysis reveals that the hybridized modes have Fano-like spectral line-shapes, which can be accurately described by a coupled oscillator model.