Propagation characteristics of the supermode based on two coupled semi-infinite rib plasmonic waveguides.

We report on the propagation characteristics of a plasmonic waveguide structure based on two coupled rectangular wedges. Dispersion, propagation loss, and field distributions are investigated by three-dimensional finite-difference time-domain method. The considered structure supports only one supermode over 30THz bandwidth, and the calculated propagation loss at lambda=1.55mum is 0.0257dB/mum, which is lower than the existing report by 1.7 times while keeping comparable field localizations. The all-planar structure in conjunction with the linearly dispersive characteristic over a wide operational bandwidth signifies its great potential for optical signal transporting in nanophotonic circuits.