Propagation Properties Analysis of a Surface Plasmonic Waveguide with Two Wedges Separated by a Nano-gap

Abstract

In this paper, a kind of surface plasmonic waveguide (SPW) with two wedges separated by a nano-gap is presented. Based on the finite element method (FEM), the dependence of the distribution of electric field magnitude, effective index, propagation length, mode area of the fundamental mode and quality factor on the geometrical parameters and the shape of waveguide is analyzed. Results show that the distribution of electric field magnitude concentrates round the tips of the two wedges. The effective index decreases while the propagation length and mode area increase with the increasing angles of the two wedges or the increasing gap between the two wedges. Comparison with the SPW with single wedge has been carried out. It has been shown that the SPW with two wedges has better propagation properties than the SPW with single wedge. According to the simulation, when the gap is 2 nm and the angles of the two wedges are 1/18π–1/4π, the propagation length is at the order of 10 μm, the mode area can decrease to 0.3–8 nm2 and the quality factor can be improved by 2–4 orders of magnitude than the single wedge SPW. Thus, it can be reasonably thought that this kind of SPW can be used in future ultradense photonic integrated circuits to avoid crosstalk or to improve the microminiaturization and integrated level. Finally, the possibility to use the SPW with two wedges in the area of sensor is discussed.