OBSERVATIONS OF 2ND-HARMONIC GENERATION FROM RANDOMLY ROUGH METAL-SURFACES

The angular distributions of second-harmonic light scattered from meta l surfaces with weak random roughness are studied experimentally. The power spectrum of the roughness has a rectangular form centered on the surface plasmon polariton wave number at the fundamental frequency, p roducing strong excitation of these surface waves. The scattering dist ributions exhibit a pair of distinct peaks at angles consistent with t he nonlinear interaction of the incident wave with fundamental plasmon polaritons. The controlled experiments allow a number of other scatte ring processes to be identified that include, for example, the nonline ar excitation of surface plasmon polaritons at the harmonic frequency. A peak in the second-harmonic distribution, predicted to appear in a direction perpendicular to the mean surface, is not observed.