RADIATIVE VIRTUAL MODES IN METAL-DIELECTRIC MULTILAYERS

Radiative virtual modes, defined as propagative modes with time dampin g resulting from the coupling of light with surface charges in metalli c thin films, are characterized and analyzed in the case of metal diel ectric multilayers of experimental interest. Modes with ''electronic'' (plasmon-like) and ''photonic'' (photon-like) character are identifie d and their observability in reflectivity spectra is discussed as a fu nction of the number of layers, the angle of incidence and the intrins ic damping in the metal.