Metallic nanoparticles on waveguide structures: effects on waveguide mode properties and the promise of sensing applications

Abstract

We present a treatment of metallic nanoparticles on waveguide (WG) structures, treating the scenario where the spacing between the metallic nanoparticles is much less than the wavelength of light. We derive an effective medium treatment of the layer containing the nanoparticles, introducing transfer matrices for the layer. The coefficients of the transfer matrices take into account the interaction of the nanoparticles with each other, as well as local field corrections to the interaction of the nanoparticles with the material beneath them. Used with the WG mode pole expansions for the Fresnel coefficients of the WG structure, this allows for simple expressions for the shift and width of the WG mode resonance wave vector induced by the nanoparticles. As an example, we work out the simple case where the nanoparticles are treated as point dipoles, and use it to investigate the potential of this kind of structure for sensing applications.