Analysis of Slot and Triangle-Shaped Surface Plasmonic Waveguides Using a Full-Vectorial Imaginary-Distance Finite-Element Beam Propagation Method

This research is devoted to analyzing the surface plasmon polariton (SPP) waveguides using the finite-element imaginary-distance beam propagation method (FE-ID-BPM). These waveguides, including symmetric/asymmetric slot waveguides as well as ideal/real triangle-shaped waveguides, have confined modal field distributions and are studied in detail. First, we introduce the history and the studies and the basic physical phenomenon of the surface plasmon as well as SPP guiding structures. Then we present our calculation results, comprising the effective index and the loss (propagation length), the modal field profiles, and the dispersion relationships. Detailed modal field profiles in different design parameter cases are displayed to observe the physical phenomenon and scout the design methods (as well as the design trade-offs). The observed results are interpreted and compared to other published works. Several interesting issues, for example, the sharp corner case of the triangle-shaped waveguide which is rarely reported, the different inclination of asymmetric slot waveguides compared to symmetric ones, and the reexamination of the mode ``cut-off" phenomenon described in published literature, are addressed and explained.