Near-field polarization of a plasmonic prolate nanospheroid in a Gaussian beam

Abstract

Analytical analysis of the near-field polarization distribution of a plasmonic prolate nanospheroid in a Gaussian beam is given. Polarization of the near-field is described with the help of the 3D generalized Stokes parameters, allowing simple visualization. It is shown that for a linearly polarized Gaussian beam with the lower mode TEM00, which falls perpendicular to the main axis of the nanospheroid, only the plasmonic mode with n = 1, m = 0 is excited, which is exactly the case of an incident plane wave. However, interaction with the Gaussian beam with a transverse mode of higher order leads to the excitation of the higher order plasmon modes, which gives a much more peculiar distribution. Received analytical solutions cover the whole set of particles with shape varying from spherical to the nanoneedles and nanorods by changing the aspect ratio of the spheroid.