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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 mu m, 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. Korea Government (MSIP)2009-0081565 Refereed/Peer-reviewed

Using finite-difference time-domain simulations it is shown that a metal-insulator-metal (MIM) ring with a narrow gap exhibits plasmonic stop bands (PLSBs) in a similar way that a microstrip ring with a narrow gap exhibits photonic stop bands. A narrow gap created in the middle of the upper half of a regular MIM ring causes plasmonic fields to experience multiple reflections at the discontinuity introduced by the gap, which results in the formation of PLSBs. The PLSBs appear as transmission dips around the resonant frequencies of the isolated MIM ring with the narrow gap. The centre frequency and the range of PLSBs are shown to be controllable by varying the width of the narrow gap. The proposed design for a MIM ring in which PLSBs exist is expected to reduce the size of the plasmonic devices.