Mode source/Plane wave source and PML or Metal boundaries.

- August 9, 2021 at 10:27 pm
  
  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.
- August 12, 2021 at 12:36 pm
  
  talimu
  Subscriber
  
  Hi gsun
  1) Let's say I have PML BC both in X and Y, so mode source size can exceed simulation size? can it be smaller than simulation size? 2) Do you have this link Ansys Insight: FDTD Solutions 的光源类型及其典型应用：初学者 in English? Thanks, talimu
- August 12, 2021 at 4:01 pm
  
  Guilin Sun
  Ansys Employee
  
  A1: I would recommend to set the mode source larger than simulation size. it has no harm doing so. However, if it is smaller, depending on the size, mode could be truncated. I believe the simulation size is proper when you set.
  A2: Sorry, it has no English version. It could be helpful if you can use goolge translate. Basically, in principle, plane wave source should have periodic-type BCs such as "periodic" and "bloch"; other sources with limited size in physics can use PML.