Direct far-field observation of surface-plasmon propagation by photoinduced scattering

A tightly focused laser beam is shown to act as a scatterer of surface plas mons. The energy released into free space due to the scattering is collecte d by far-field optics. Scanning the laser beam over the plasmon field gives a map of their propagation. Evidence is given which shows that the surface -plasmon map gives much more detail of plasmon propagation and film structu re than the photothermal image, which monitors the heat deposited during pl asmon propagation. (C) 1999 American Institute of Physics. [S0003-6951(99)0 0751-2].