Plasmon resonances of spherical and ellipsoidal nanoparticles

Surface plasmon resonance (SPR) of a single metallic nanoparticle is analyzed and simulated via multi-multipole method for 3D problems. The excitation, at optical frequencies, of the SPR leads to an extremely strong field in the vicinity of the nanoparticle. Numerical results indicate that a red shift of SPR is induced for an ellipsoidal nanoparticle, compared to a spherical one. Two structures of core-shelled spherical nanoparticles are also studied; one is a nanosphere of Ag shell with an oxide core, and the other one is Ag core with an oxide shell (ZrO₂ or SiO₂). Numerical results illustrate the SPR of these two core-shelled structures are quite different from each other and different from that of a solid one. It suggests that one can manipulate the optical response on demand by tuning the core/shell ratio and the permittivity of shell or core.