A silicon-based hybrid plasmonic waveguide with a metal cap for a nano-scale light confinement

A hybrid plasmonic waveguide with a metal cap on a silicon-on-insulator rib (or slab) is presented. There is a low-index material nano-layer between the Si layer and the metal layer. The field enhancement in the nano-layer provides a nano-scale confinement of the optical field (e.g., 50 nm x 5 nm) when operates at the optical wavelength lambda = 1550 nm. The theoretical investigation also shows that the present hybrid plasmonic waveguide has a low loss and consequently a relatively long propagation distance (on the order of several tens of lambda).