We show numerically that the size of the nanoparticles (NPs) that scatter surface plasmon-polaritons (SPPs) is directly related to the angular position of the maximum in a scattered light distribution. Thus, the existence of one or two experimentally observed maxima in the angular distribution of the scattered light for different NP materials can be explained by a bimodal NP size distribution. We also invoke the polarization properties of the scattered light to estimate the contribution of multiple scattering processes to the observed light distribution. SPP excitation can be detected by a minimum in the reflectivity, or a maximum in the scattered light distribution. We show that this maximum exists for a wider range of NP sizes (or surface roughness) than the minimum in the reflectivity. This observation is interesting for the development of SPP based optical sensors.
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