A Slot-Based Surface Plasmon-Polariton Waveguide With Long-Range Propagation and Superconfinement

A full-vector spectral element method (SEM) is applied to model and simulate surface plasmon-polariton (SPP) waveguides. Gauss-Lobatto-Legendre (GLL) polynomials are used to construct higher-order basis functions to achieve spectral accuracy. A discretization scheme featuring a nonuniform mesh with extra elements near the metal-dielectric interface is proposed to capture the waveguide configuration and dramatical mode field variations of the SPP waveguide. The studies on the accuracy and mode field distribution show that SEM is highly efficient and accurate. Using SEM simulation, a slot-based SPP waveguide operating at telecom wavelengths is proposed. Numerical results show that the proposed structure can simultaneously achieve millimeter-scale propagation distance (L_p ~2.6 mm) and below-diffraction-limited effective mode area (A_eff/A₀ ~0.3) . Parametric plots illustrate a significant improvement when compared to conventional SPP waveguides. Investigation of the mode width and crosstalk also demonstrates the excellent 3-D integration performance of the structure. The proposed slot-based SPP waveguide thus can become a potential candidate for highly integrated photonic circuits.