Modeling interface discontinuities and boundary conditions for a dispersion-optimized finite-difference time-domain method

This article describes extensions to a dispersion-optimized finite-difference time-domain (FDTD) method for analysing long-range propagation problems. We examine the handling of boundary condition problems produced by inhomogeneous materials and FDTD grid truncation. Truncation of the simulation grid is accomplished by using a uniaxial perfectly matched layer absorber coupled with the dispersion-optimized fourth order differences. Material discontinuities require a modification of the higher order FDTD updates at the material interfaces; the exact modifications can be derived by enforcing continuity of multiple derivatives at the material interface.