Modal analysis of LSP propagation in an integrated chain of gold nanowires

Light propagation in an integrated chain of metallic nanowires (MNW) is theoretically investigated by means of rigorous coupled wave analysis. First, we analyze the nanowires chain immersed in a dielectric homogeneous medium and we compute the eigenmodes dispersion relation and their field profiles. Depending on the nanowire aspect ratio, in addition to the longitudinal and the transversal chain modes, we found a new mode characterized by quadrupolar-like localized surface plasmons resonances well identified at the edge of the first Brillouin zone. We then consider the vertical coupling of the MNW chain with the fundamental TM0 mode of a planar dielectric waveguide. We demonstrate that high energy transfer can be obtained, by computing near field maps and spectral responses (transmission, reflection, and absorption) of the structure consisting in a finite number of nanowires. The coupling mechanism between the dielectric waveguide and the MNW chain is rigorously explained through the analysis of the eigenmodes dispersion relation.