Abstract
In this paper, we present a full-vector finite difference method to solve for optical modes in one and two dimensional subwavelength plasmonic waveguides. We have used the Implicitly Restarted Arnoldi method to directly calculate the propagation constants of the dominant modes. The method has low computational complexity and can be applied to accurately model complex geometries and structures with fast-varying field profiles. When applied to solve for purely bounded modes, our method automatically separates evanescent and low-loss guided modes.