Nanoscale light guiding in a silicon-based hybrid plasmonic waveguide that incorporates an inverse metal ridge

A silicon-based hybrid plasmonic waveguide that comprises an inverse metal ridge sitting above a silicon-on-insulator substrate with a nanometre-thick, low-index gap is proposed and its guiding mode properties are analyzed numerically at the wavelength of 1,550 nm. The strongly hybridized modes supported by the inverse metal ridge and the thin silicon layer provide an efficient scheme to store the optical field inside the nanoscale gap region with strong local field enhancement. Compared to the previously studied hybrid plasmonic waveguides based on the coupling between metal wedges or metal ridges with finite-wide high-index nanowires, the present hybrid waveguide leveraging inverse metallic wedge with infinite-wide silicon layer simplifies the fabrication process to a certain extent and avoids the lateral misalignment that is rather challenging to control in many other hybrid plasmonic waveguiding counterparts. Besides, the studied structure also shows the potential to further reduce the mode size of conventional hybrid waveguide based on flat metal substrate, thus making itself an attractive building block for compact photonic integrated components and circuits.