Electromagnetic fields around silver nanoparticles and dimers

The discrete dipole approximation was used for analyzing the electromagnetic fields induced by optical excitation of localized surface plasmon resonances around the silver nanoparticles, monomers and dimers. The particle size, shape and arrangement that led to the largest local electric field (E-field) enhancement near the particle surfaces were determined. It was found that enhancement is a strong function of separation distance and it scales with particle size, such that larger particles give the same enhancement for larger separations. The results show that the plasmon resonances that led to the largest E-fields were those with the longest wavelength dipolar excitation.