Boundary element method applied to the analysis of the response of coupled nanoparticles

The boundary element method is a versatile tool for describing the interaction of light with micro- and nano-structured objects having a closed contour. We present an extension of the classical algorithm, which is capable of treating problems consisting of more than a single scatterer. To do so, we write the incident field on an object as the superposition of the incident source field on particle and a contribution from the scattered field from every other particle that the system consists of. A system of linear equations is derived which solves the problem for all particles simultaneously. Its advantage over other computational schemes such as iterative procedures is discussed. In the first calculations we have applied the method to coupled silver nano-particles. Illuminating the particles at appropriate wavelengths will excite surface plasmons. Plasmon excitation will lead to a resonantly enhanced near-field amplitude and a large scattering cross section (SCS). The scattering properties will change if additional particles are present in the surrounding.