Unidirectional excitation of surface plasmons by slanted gratings

Surface plasmon excitation by normally incident light on surface-relief metallic diffraction gratings is studied numerically. Predominantly unidirectional excitation is achieved with a grating of either a slanted lamellar or an inclined sinusoidal groove profile, both having shallow depths. Maps of Poynting vector illustrate that the energy flow turns from normal incidence in the far-field region to a pattern almost parallel to the grating surface in the required direction of excitation of a single SPP wave.