Plasmonic Coupler for Silicon-Based Micro-Slabs to Plasominc Nano-Gap Waveguide Mode Coversion Enhancement

We investigate a short (~1.5 μm) “partially” corrugated tapered waveguide for silicon-based micro-slab waveguide to plasmonic nano-gap waveguide mode conversion at the optical communication frequency. The structure is designed to achieve more precise mode matching between the silicon slabs and plasmonic waveguides. High transmission efficiencies up to 87%~98% have been demonstrated numerically. The results show that the corrugated structure should not only be helpful for realizing full on-chip silicon plasmonic devices but also a good choice for mode coupling enhancement from dielectric waveguides to plasmonic waveguides. Meanwhile, we point out that the coupling mechanism reported here is different from that achieved by exciting surface plasmon polaritions (SPPs) at metal surfaces reported in the literature [18], [19].