Directional coupler based on an elliptic cylindrical nanowire hybrid plasmonic waveguide

摘要

We present what we believe is a novel directional coupler based on an elliptic cylindrical nanowire hybrid plasmonic waveguide. Using the finite element method, the electric field distributions of gamma-polarized symmetric and antisymmetric modes of the coupler are compared, and the coupling and transmission characteristics are analyzed; then the optimized separation distance between the two parallel waveguides, 100 nm, is obtained. This optimized architecture fits in the weak coupling regime. Furthermore, the energy transfer is studied, and the performances of the directional coupler are evaluated, including excess loss, coupling degree, and directionality. The results show that when the separation distance is set to 100 nm, the coupling length reaches the shorter value of 1.646 mu m, and the propagation loss is as low as 0.076 dB/mu m, and the maximum energy transfer can reach 80%. The proposed directional coupler features good energy confinement, ultracompact and low propagation loss, which has potential application in dense photonic-integrated circuits and other photonic devices. (C) 2018 Optical Society of America