Metal-coated hollow nanowires for low-loss transportation of plasmonic modes with nanoscale mode confinement

Two types of plasmonic waveguiding structures based on hollow dielectric nanowires are proposed and their modal properties are investigated numerically at a wavelength of 1550 nm. The first type of waveguide consists of a high-index hollow nanowire covered directly by a thin metallic film. Depending on the size of the hollow nanowire, such a waveguide could support a plasmonic mode with lower propagation loss than the metal-coated nanowire structures without a hollow core. To further reduce the propagation loss, a second type of waveguide is proposed, which includes an additional low-index silica buffer layer between the metal layer and the hollow nanowire. Simulations reveal that the additional low-index buffer could enable strong hybridization between the dielectric mode and the plasmonic mode, which leads to even lower propagation loss while maintaining nanoscale confinement similar to that of the first type of waveguide. Both of the proposed waveguides are feasible using modern fabrication methods and could facilitate potential applications in integrated photonic components and circuits.