Low-loss ultra-subwavelength hybrid plasmonic waveguide based on metallic bump structures

Sharp metal edges (like wedge or triangular geometries) have been widely studied as low-loss surface plasmon polariton (SPP) waveguiding structures. However, fabrication difficulties lead to round-shaped tips which have larger mode size and shorter propagation length. As a solution, here we present an easy to realize structure for turning an edge-less bump metallic geometry (whose fabrication is less troublesome) into a hybrid one. Through investigating the geometrical dispersion, propagation lengths of up to half a millimetre and effective mode areas as small as lambda(2)/330 are obtained for the 1.55 mu m telecommunication wavelength. Gain-assisted SPP propagation is also considered by introducing gain in the InGaAsP material, for which critical gain as low as 11 cm(-1) is calculated. Finally, obtained results suggest that the designed waveguide can find various applications in nanoscale waveguiding.