Second-Order Mode Analysis of Spoof Surface Plasmon Waveguide

This paper analyzes the second-order mode of the spoof surface plasmon (SSP) waveguide, which consists of PEC pillars (dominos) with finite lateral widths on a PEC ground. The space is first divided into four regions. The electromagnetic fields of each region are then written as TE and TM. The boundary conditions and matching integrals are employed to determine the dispersion relations of the second-order mode of the SSP waveguide consisting of two relations. Inspired by Marcatili’s method, the analytical approach is to develop a recently-used method for the first mode of the SSP waveguide. The dispersion relations are then solved; therefore, the dispersion curve is plotted. The analytical results compared with numerical results of a commercial numerical eigensolver. The mean error is defined and plotted for different parameters of dimensions, on which the mean error of dispersion depends. According to the results, the mean error was below 5% in certain conditions.