Directionally scattered optical second-harmonic generation with surface plasmons

The spatial distribution of scattered optical second-harmonic generation owing to prism-coupled surface plasmon excitation at a silver-quartz crystal interface is studied. This spatial pattern, which has the shape of a limited arc radiated in the direction normal to the interface, can geometrically be explained in terms of the beating between the forward incident and backward scattered surface plasmons. The observed intensity distribution of the scattered harmonic light cannot be fitted by a single-scattering theory; thus the dominant contribution to the scattering arises from multiply scattered surface plasmons that may be interpreted in terms of enhanced backscattering.