We theoretically study the features of the surface-plasmon-polariton (SPP) excitation on single or chains of spherical metal nanoparticles located near a metal surface with an inclined incident light beam. It is found that by tuning the incident angle of an external light beam and the parameters of the surface nanoparticle structures one could obtain symmetric or asymmetric excitation of SPP beams propagating into certain directions. The reasons and conditions for this behavior and the efficiency of SPP excitation as a function of the incident angle are discussed.
A theoretical model of the interaction between finite mesoscopic objects within the layer structure situated on a substrate and the light in the near-field zone is presented. Consideration is based on a set of self-consistent integral equations for the electric field obtained from the Maxwell equations using a Green-function technique. In the work we give special attention to constmct in the quasi-electrostatic approximation the dyadic Green's function of the reference system, which includes the substrate and the solid layer embedded in an infinite homogeneous medium. Our approach also allows us to construct the Green's function for two mediums with plane interface. We use unretarded approximation due to the fact that the distances between all points, which are included in the consideration, are assumed to be much smaller than the wavelength of the light in SNOM. On the base of this approach we obtain the analytical expression of the dyadic Green's function in direct space and numerically calculate the distribution of electric field intensity in the system. We consider two SNOM configurations. We show that the layer structure and substrate may play significant role in image formation. In the work we also discuss the scattering problem of longitudinal surface polaritons in SNOM of the collection configuration.
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