Evanescent coupling to silicon waveguides using surface plasmon polaritons.

In this work, we discuss evanescent light coupling to silicon waveguides using surface plasmon polaritons (SPPs) in the Otto configuration. The setup for excitation of SPPs includes a fused-silica prism, a 100 nm silver layer with a 650 nm airgap between them, and a tapered silicon waveguide located across from the silver layer. A $p$p-polarized light of 1550 nm wavelength is incident at plasmonic angle of 44° to the interface of the fused silica-airgap to excite the SPP. A 2D Lumerical FDTD Solutions simulation shows a coupling efficiency of 54%. The fabricated device on a silicon-on-insulator substrate shows 10% light transmission for $p$p-polarized light.