An apparatus and corresponding method in which the apparatus includes a dielectric waveguide and a metallic waveguide. The dielectric waveguide has an effective mode index and a longitudinal dimension. The metallic waveguide has a longitudinal dimension and supports a surface plasmonic mode of propagation for a wavelength lambda. The metallic waveguide and the dielectric waveguide are adjacent to each other and overlap each other by a length along the longitudinal dimensions of both the dielectric waveguide and the metallic waveguide, wherein the length is greater than the wavelength lambda in the metallic waveguide. The metallic waveguide is coupled to the dielectric waveguide where the metallic waveguide and the dielectric waveguide overlap each other.