Extinction spectra and near-field enhancement of metallic nanoparticles

Extinction spectra and near-field enhancement of metallic nanoparticles are calculated with a boundary integral equation (BIE) method. With the BIE method the far-field response and the near-field evanescent coupling are expressed as an eigenmode sum of resonant terms. In particular, the near-field enhancement around nanoparticles is obtained as a sum of resonant terms which acquire the spatial dependence of the eigenfunctions of the BIE operators. Moreover, the presented method permits a direct link between near-field and far field spectral properties. Finally, a numerical example is given.