Abstract

Optical second-harmonic generation at surface is a very sensitive and interface specific spectroscopic tool. This technique is based on the fact that the second order nonlinear optical processes are forbidden inside a centrosymmetric medium, but are allowed at the surface, where such a symmetry is broken. Molecules adsorbed at metallic surface produce enhancement of second order nonlinearities. Due to location of a deep of interference pattern of incident and reflected waves at the metal surface, the role of surface polaritons in the second-harmonic generation is very important. Excitation of surface polaritons, which are localized at the interface, by means of prism or diffraction grating leads to enhancement of the second-harmonic signal. This excitation of surface polaritons on "permanent" diffraction grating is connected with appearance of Wood's anomalies of the "leaky-wave resonance" type [1]. At these anomalies propagating fundamental and second-harmonic diffraction orders consist from two contributions, i.e. nonresonant Fresnel contribution and resonant leaky-wave one related to excitation of surface polaritons on the grating [2].

© 2000 IEEE