Plasmonic behaviors of gold dimers perturbed by a single nanoparticle in the gap.

Modulation of resonance modes of plasmonic nanostructures at a single nanostructure level is of great importance for the development of integrated photonic chips. Recent progress of the fabrication techniques including double electron beam lithography, direct laser printing, and electron beam induced deposition has allowed the local fabrication of sub-50 nm size nanoparticles (NPs) of various materials, which provides a potential experimental realization of local impact on plasmonic behaviors of single nanostructures. In this article, we theoretically investigate that the presence of a single NP in the midgap may give rise to the excitation of new resonance modes and/or large spectral shifts of resonance modes for different plasmonic dimers (gold bowtie, nanodisk and nanorod dimers), therefore resulting in the modification of the far-field and near-field optical properties. The modification can be controlled by changing the deposition position, particle size, and material composition of the single NP. Moreover, our calculations imply that the plasmonic dimers perturbed locally by a single NP of the metal-insulator phase transition material (vanadium dioxide) in the gap can potentially act as very effective optical switch components in future photonic chips.