Plasmons excited by an evanescent wave in a periodic array of nanowires

Unusual plasmons, excited by an evanescent wave in narrow slits in a periodic array of nanowires overlying a dielectric substrate, are found from Maxwell's equations by a modified boundary element method. The evanescent wave appears when the incident plane wave runs onto the boundary from the substrate under the angle of total internal reflection. On the basis of Floquet's theorem, the effective Green's function is derived by reducing the infinite structure to one elementary cell. The method is tested by simulation of the known Rayleigh-Wood's anomalies. The plasmon resonance is found to have a sharp dependence on the angle of incidence.