High-order effects in the scattering of light due to plasmon polariton excitation on metal surfaces

摘要

If a metal surface has a roughness of a few nanometers, an incident light wave may excite the surface waves known as surface plasmon polaritons. In turn, the plasmon polaritons may themselves be outwardly surface-coupled to produce effects in the light escaping from the surface. Here, the polariton-related effects in both the fundamental and second-harmonic emitted light are considered. In the linear case, a theoretical approach is developed that allows the polaritons to be scattered several times within the surface before coupling to diffuse light escaping from the surface. In the diffuse scatter emitted by a randomly rough surface, these high-order processes are shown to produce changes in the shape and width of the backscattering peak. In experimental results for the emitted second-harmonic generation, it is found that the features are dominated by the contributions of polaritons at both the fundamental and harmonic frequencies. These nonlinear wave interactions are illustrated with experimental results for randomly rough and for quasiperiodic surfaces.