Guilin Sun
Ansys Employee
Sources can only work with proper boundary conditions in order to fulfill physics. Mode source has limited size so it uses PML or sometimes PEC; Plane wave is infinite so periodic-type BC or symmetry-type ( PEC/PMC in some cases) BC in both sides is used. Please refer :Ansys Insight: FDTD Solutions 的光源类型及其典型应用:初学者 Please note that for mode (and Gaussian) source, its geometry size can be as large as the simulation spans. This is because the mode property controls the physical size.