Geometric dependence of metal-coated silicon nanowire plasmonic waveguides

We report the geometric dependences of metal-coated silicon nanowire (Si NW) plasmonic waveguides on their propagation lengths and mode areas. We examined Si NWs with four different cross-sectional shapes. Numerical simulations showed that propagation lengths and mode areas are highly dependent on the cross-sectional geometries of Si NWs. In particular, the TM-like mode in a hexagonal-shaped Si NW plasmonic waveguide without an air void has the longest propagation length of 18.20 μm, which is 4.7 times larger than that of the TM-like mode in a circular-shaped Si NW plasmonic waveguide. This study can be a useful guide for the design and application of metal-coated Si NW plasmonic waveguides.