INTERFERENCE OF LOCALLY EXCITED SURFACE-PLASMONS

Surface plasmon interactions on a finite silver layer are theoreticall y investigated using a coupled dipole formalism. The studied system co nsists of several protruding particles located on the surface of the l ayer that are scanned with an optical probe. An optical scan-image of the silver surface is obtained by assigning the recorded far-field rad iation to the momentary position of the optical probe. Both, probe and protrusions are considered as single dipolar panicles. Interferences of the locally excited surface plasmons can be recorded by detecting t he radiation emitted into the lower half-space at angles beyond the cr itical angle of total internal reflection (forbidden light). The resul ting scan images show excellent agreement with recent experimental mea surements. The theory of the coupled dipole formalism using Green's fu nctions of a layered reference system is outlined and electromagnetic properties of surface plasmons are discussed. (C) 1997 American Instit ute of Physics.