Dependence of plasmon coupling on curved interfaces.

The optical properties of coupled plasmon systems can be tuned by individual material and geometry, gap distance, and surrounding dielectric. This paper reports a dramatic effect of a curved interface in the nanoparticles dimer on the optical responses. Compared with gold nanorod (AuNR) monomer, AuNR dimers with different assembly types (such as end-to-end and side-by-side) can manipulate the longitudinal surface plasmon resonance (SPRL ) to red/blueshift. The electromagnetic field of the dimer is further enhanced in the interactive region. Under the incident polarization along the gap, a new resonance mode will be excited when AuNR dimers touch each other, and the SPR mode turns to blueshift from redshift due to the formation of the conductive coupling. It can be assumed that when one of the interactive surfaces is curved, an additional plasmon resonance can be stimulated under the polarization of incident light along the gap. The particular phenomenon can be explained by the plasmon hybridization theory. Silver nanocubes dimers (with sharp or smooth corners and edges) also possess the same property. Supported by finite-difference time-domain solutions, the coupled plasmon resonance mode represents high sensitivity to structural geometry.