Manipulation of surface plasmon-polaritons in nanocomposite-metal-nanocomposite waveguide

Abstract

We investigate the dispersion characteristics of surface plasmon-polaritons (SPPs) in a nanocomposite-metal-nanocomposite waveguide. Due to the coupling between propagating and localized surface plasmons, the wave vectors of long-range surface plasmon (LRSP) and short-range surface plasmon (SRSP) modes in the proposed waveguide can be greatly enlarged in comparison to a simple insulator-metal-insulator (MIM) geometry. This leads to intense spatial confinement of the gap modes by suppressing their wavelengths. We demonstrate that the mode that can travel infinitely large distances is the LRSP, but the mode with strong spatial confinement is the SRSP. The wavelengths of the two modes can be further reduced with increasing the ratio and size of the nanoparticles, and thickness of the central metal film, offering a set of parameters to manipulate the properties of gap plasmons. The study presents and compares results for SPPs with two different metal-dielectric composites in silver-silica and gold-alumina configurations.