Low-loss hybrid plasmonic waveguide based on metal ridge and semiconductor nanowire

A novel hybrid plasmonic waveguide (HPW) based on a metal ridge and a semiconductor nanowire is proposed and analyzed theoretically. The high-index cylinder semiconductor nanowire is placed above a metal substrate with a semi-cylinder metal ridge and the low-index dielectric gap between them is introduced for nanoscale field confinement. Our simulations show that mode area as low as λ2/1600 which is about three orders of the magnitude smaller than the diffraction-limit area in free space has been achieved for the proposed HPW. Compared with the early reported HPW with a high-index nanowire placed above a flat metal substrate without a semi-cylinder metal ridge, the proposed HPW has more tight lateral confinement and longer propagation distance, which also improves figure of merit (FOM). The propose HPW with truly nanoscale field confinement and low propagation loss has potential in applications such as low-threshold lasers.