Excitation and direct imaging of surface plasmon polariton modes in a two-dimensional grating

We describe the simultaneous excitation and direct far-field imaging of the scattering from surface plasmon polariton modes in a two-dimensional metallic hole array grating. Conditions for the coupling and imaging are discussed, where the coupling is shown to be consistent with both measured and calculated dispersion relations. Excitation is accomplished at several different wavelengths (from 1.31 to 1.57μm), incidence angles, and grating periods, enabling the observation of a number of distinct modes with various in-plane wave vectors.