Numerical Modelling for the Analysis of Plasmon Oscillations in Metallic Nanoparticles

This work is focused on the numerical modeling, in the frequency domain, of the plasmon oscillations induced in metallic nanoparticles of arbitrary shapes by an external electromagnetic field. The electromagnetic response of the nanoparticles is modeled through a proper frequency dependent dielectric constant. The electromagnetic field scattered by the nanoparticles is evaluated by a full-wave integral formulation where the unknown is the induced current density. The integral equations are solved numerically by the finite element method, by decomposing the current density in the solenoidal and non-solenoidal components and using the edge-elements. Particular care has been devoted to treat, within such numerical method, arbitrary topologies. A detailed analysis is carried out to understand the limit of applicability of the electro-quasi-stationary model and a characteristic length lm of the metal, together with the wavelength of the electromagnetic field, are found to provide a constraint on the maximum nanoparticle size that can be treated within such approximation.