Finite-difference time-domain is a popular computational electrodynamics modeling technique. It is considered easy to understand and easy to implement in software. Since it is a time-domain method, solutions can cover a wide frequency range with a single simulation run. The FDTD method belongs in the general class of grid-based differential time-domain numerical modeling methods. The time-dependent Maxwell's equations l are discretized using central-difference approximations to the space and time partial derivatives. The resulting finite-difference equations are solved in either software or hardware in a leapfrog manner: the electric field vector components in a volume of space are solved at a given instant in time then the magnetic field vector components in the same spatial volume are solved at the next instant in time; and the process is repeated over and over again until the desired transient or steady-state electromagnetic field behavior is fully evolved. The basic FDTD space grid and time-stepping algorithm trace back to a seminal 1966 paper by Kane Yee in IEEE Transactions on Antennas and Propagation. The descriptor Finite-difference time-domain and its corresponding FDTD acronym were originated by Allen Taflove in a 1980 paper in IEEE Transactions on Electromagnetic Compatibility for these and other important journal papers in the development of FDTD techniques, as well as relevant textbooks and research monographs. Since about 1990, FDTD techniques have emerged as primary means to computationally model many scientific and engineering problems dealing with electromagnetic wave interactions with material structures. As summarized in Taflove & Hagness, current FDTD modeling applications range from near-DC through microwaves to visible light. In 2006, an estimated 2,000 FDTD-related publications appeared in the science and engineering literature