Guilin Sun
Ansys Employee
non-zero transmission is because the monitor is not on the Bloch Boundary. In physics power cannot just go in one direction on the sides that are periodic when periodic BCs are used. Bloch BC is a generalized periodic BC.
For your purpose, you may need to check the slab mode using FDE instead of using power monitor in FDTD. I would suggest that you consider the physics carefully.