Coupling and guided propagation along parallel chains of plasmonic nanoparticles

We derive a dynamic closed-form dispersion relation for the analysis of the entire spectrum of guided wave propagation along coupled parallel linear arrays of plasmonic nanoparticles, operating as optical 'two-line' waveguides. Compared to linear arrays of nanoparticles, our results suggest that these waveguides may support more confined beams with comparable or even longer propagation lengths, operating analogously to transmission-line segments at lower frequencies. Our formulation fully takes into account the entire dynamic interaction among the infinite number of nanoparticles composing the parallel arrays, considering also the realistic presence of losses and the frequency dispersion of the involved plasmonic materials, providing physical insights into the guidance properties that characterize this geometry.