An effective excitation of the lightwaves in the plasmonic nanostrip by way of directional coupling

초록

A guided-wave directional coupler is proposed for an effective excitation of the lightwaves in the plasmonic nanostrip, as shown in Fig. 1(a). A silicon nanowire (NW) is used for the lightwave coupling. The guided-wave coupler is designed based on the matching of the effective refractive indices of the two waveguides, using 3-D finite element method. The mode profiles of the even mode and the odd mode in the guided-wave coupler are analyzed by 2-dimentional (2-D) finite element method (FEM). The mode of energy transfer between the two waveguides, as solved by 3-D FEM is depicted in Fig. 1(b). Also, to optimize the couplers the beat length of the guided-wave coupler is analyzed with respect to the width of the plasmonic nanostrip. From this analysis we obtain the minimal beat length of the guided-wave coupler and the lowest excitation loss with respect to the width. This study provides not only a way of minimizing the coupler length and the excitation loss for effective excitation of the plasmonic nanostrips but also a way of integrating the plasmonic nanostrips and dielectric nanowires for nano-photonic integrated circuit application.