p-polarized optical properties of aggregated Au films

Transmittance with p-polarized light at oblique incidence has been measured for aggregated Au films in the region from 0.40 to 0.65 μm. At large values of the incidence angle, two minima associated with the perpendicular and parallel plasma resonances in the particles were observed. The dependence of these absorption features on film characteristics was accounted for by a simple effective medium model assuming a spheroidal shape for the particles. In this model, the substrate effect has been incorporated by mirror-image contributions of the induced dipoles. A log-normal distribution for the axial ratio was assumed in order to take into account the broadening of the absorption characteristics. Satisfactory agreement between theory and experiment has been obtained using only the optical thickness as a fitting parameter, and assuming a certain standard deviation for the log-normal distribution.