Abstract
Exact absorbing boundary conditions (EACs) for highly-accurate modeling of transient electromagnetic waves interaction on 3-D diffraction gratings are rigorously derived. EACs when enforced together with periodic boundary conditions permit the truncation of the infinite physical domain of the gratings to a bounded computation domain without introducing any additional errors. Numerical results demonstrate that discretization error of the EACs matches the error of the method used of discretizing the Maxwell equations, and therefore suggest that EAC-based truncation might result in more accurate or efficient simulations when compared to PML-based truncation.