Frequency- and polarization-dependent optical response of asymmetric spheroidal silver nanoparticles on dielectric substrate

We report theoretical simulations of plasmonic near-field enhancement and polarization in a system consisting of an asymmetric spheroidal Ag nanoparticle on a smooth dielectric surface. Finite-difference time-domain (FDTD) simulations reveal resonant optical extinction bands whose near-field is concentrated at the metal–substrate contact point with intensity enhancement by a factor of 103 and predominant polarization along the normal to the surface. These features may help explain enhanced photo-catalytic activity observed for colloidal Au and Ag nanoparticles on titania substrates