Observation of long range surface plasmon decay length by optical second harmonic generation

We report the observation of the spatial decay of the long range surface plasmon mode using optical second harmonic generation. The surface wave is excited at 1.06 microm with prism coupling in a multilayer geometry consisting of a quartz crystal substrate, a thin silver film, and an index-matched liquid. From the asymmetry in the reflected second harmonic profile a decay length of 0.8 mm is determined. This value is a factor of 3 smaller than that predicted due to the effect of surface roughness scattering on the propagation of the long range surface plasmon mode.