Near field by subwavelength particles on metallic substrates with cylindrical surface plasmon excitation

The near electromagnetic field scattered by a spherical subwavelength particle on a flat metallic substrate is calculated when the incident light is a plane monochromatic linearly polarized wave. The complete solution to the scattering problem that we consider includes the possible surface wave components of the field. Cylindrical surface plasmon-polaritons are shown to be excited by the particle on the substrate when this is metallic and the particle is close enough. The shape of the field associated to the surface plasmon-polariton depends on the incident polarization and angle of incidence. In a real situation, the plasmon field interferes with the incident field. The spatial distribution of the interference pattern is analyzed in terms of the incident polarization and the angle of incidence and differences from the case of bulk propagating waves are shown. Incident polarization parallel to the plane of incidence is proved to be more efficient than the perpendicular one for surface plasmon generation because of the vertical component of the particle dipole moment. The propagation characteristics of the cylindrical surface waves (wave number, phase) are obtained from the interference pattern.