The optical excitation of propagating surface plasmons on metal films is most commonly accomplished by the prism coupling method (Kretschmann configuration). More than 25 years ago, it has been demonstrated that surface plasmons can also be excited by nonlinear means. These nonlinear studies have concentrated predominantly on second-order processes, such as second-harmonic generation and sum-frequency generation. The reason for using second-order processes lies in its simplicity and the ability to discriminate the bulk response from the surface response using the inversion symmetry of most metals. For third-order processes it can be expected that the bulk response strongly dominates over the surface response. However, in this presentation we show that, despite of the bulk response, the surface nonlinearity is a dominating contribution in four-wave mixing in metal films.
© 2008 Optical Society of AmericaPDF Article