Efficiency-Improved 3-D WCS-FDTD Algorithm for Periodic Structures at Oblique Incidence

For solving the problems of oblique incident wave on periodic structures, an efficiency-improved 3-D weakly conditionally stable finite-difference time-domain (WCS-FDTD) method is presented in this letter, whose Courant-Friedrichs-Lewy (CFL) stability condition is only determined by one space step size. By expressing the extra terms caused by the phase delay as the form of the coefficient matrix, and combining with the locally one-dimensional (LOD) scheme and the inverse matrix operator, the Maxwell's equations are split into two sub-step procedures. Further, by introducing a set of auxiliary field variables denoted by ψ, the proposed algorithm is reformulated in a much simpler form with more concise right-hand sides for an efficient implementation. Numerical example demonstrates that the proposed method is more efficient while keeping the same CFL stability condition and memory storage requirement as that of the existing method.