Nonlocal effects in the optical response of composite materials with metallic nanoparticles

A phenomenological model for the optical response of composite materials with metallic nanoparticles is presented. This model applies the conventional effective medium theories (EMT) but takes into account the spatial dispersion effects in the dielectric response of the metallic nanoparticles. This leads to an EMT that depends on the size of the particles. Numerical results from a model computation shows that this effect due to the nonlocal optical response of the nanoparticles can increase the resonant absorption frequency of the composite significantly for particles of very small sizes; and can lead to resonant absorption even in the Bruggeman symmetric EMT-a feature which is believed to be absent in the conventional treatment where local response for the metal particles has been assumed.