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 wave guides. 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 wave guides to plasmonic wave guides. 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 ,.
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