Scattering enhancement from an array of interacting dipoles near a planar waveguide

We develop a theory for light scattering from a random array of nanoparticles spaced much less than an optical wavelength from an optical waveguide. We deal with the randomness in the particle positions by convolving the single-particle Green’s dyadic with a correlation function that describes the average properties of the particle distribution. This allows us to treat free-space and substrate-mediated particle–particle interactions. We show that coherent interactions between particles near a waveguide cause dramatic, qualitative changes to the particle susceptibilities. Hence, the scattering spectra show strong, surface-induced peaks that we associate with the onset of leaky guided waves of the layered substrate. Our predictions produce outstanding agreement with the scattering experiments of Stuart Hall [Phys. Rev. Lett.80, 5663 (1998)].