Local plasmon resonances of metal-in-metal core-shells

We investigate the tunability and strength of the localized surface plasmons of binary metal-in-metal core-shells. Ellipsoids are used as an analytical model to show how the fill factor continuously tunes a hybridized mode between those of the constituents, suggesting the use of metal combinations with widely differing plasma frequencies for broad tunability. A quasistatic eigenmode method is used separate geometric and material parameters to facilitate prediction of hybridized dipole modes in arbitrary shapes. A modified ellipsoid model is found to adequately describe the symmetric dipole-dipole resonance of well-rounded cuboids.