Boundary elements and surface plasmons

We present an elementary introduction to the boundary element method (BEM). We use the BEM to calculate the electromagnetic field enhancements in the vicinity of metallic wires of arbitrary cross-section. The local electric field shows resonant peaks, as a function of the frequency of incident radiation, at the natural frequencies of the electronic plasma in the wires. We consider the effect of the shape of the cross-section of the wire on the resonant frequency, the proximity effect due to neighboring wires, and the influence of a substrate. The calculations are performed using enhanced continuity conditions at the boundaries. We discuss the advantages of such an approach. The field enhancements are predicted for a number of geometries. copyright 1996 American Institute of Physics