Modal Analysis of Nanoplasmonic Multilayer Spherical Resonators

The resonance wavelengths, quality factors, and electromagnetic field profiles of multilayered metal plasmonic nanospheres are presented. Quantitative results are obtained using a recently developed finite-difference time-domain algorithm suited for structures with spherical invariance. The resonance modes of multilayered metal plasmonic nanospheres are explained as hybrid modes consisting of surface plasmon polariton resonances associated with each metal-dielectric interface. Multilayered metallic nanospheres exhibit complicated and numerous modes as the number of layers increases; however, the highest quality factor hybrid modes are those associated with the odd-like modes of each individual metal layer. Applications in nanoplasmonic lasers are highlighted.