Split-Step Finite-Difference Time-Domain Method with fourth order accuracy in time

This paper presents an unconditionally stable split-step finite-difference time-domain (SS-FDTD) method with 4^th order accuracy in time. Analytical proof of its unconditional stability is provided and numerical dispersion results are shown. Compared to the 2^nd order SS-FDTD, the 4^th order SS-FDTD yields a lower phase velocity error. Compared further to the 2^nd order SS-FDTD with three iterations (for the same number of time marching steps), the 4^th order SS-FDTD still achieves better numerical dispersion performance with sufficiently fine mesh.