Nanoshells with a gain layer: the effects of surface scattering

The optical properties of layered nanoparticles containing at least one metallic layer and one gain medium layer are calculated. The mean free path effect, resulting from the surface scattering of the conduction electrons, is taken into account in the usual way, by modifying the dielectric function of the metallic shell. There exist in the literature a number of effective mean free path model choices for the shell geometry. We investigate the dependence of the optical spectra, as well as the critical gain values, on the choice of the surface scattering model.