Hello Rainer,
We moved your post over to the OptiFDTD channel as this does seem to be the product you are discussing. There are three options:
- Run the waveguide right into the boundary of your simulation and set the boundary condition to the Perfect Electric Conductor (PEC).
- Add PEC as a material to your simulation and terminate your waveguide with either a short waveguide of PEC (2D) or with a Block (3D).
- If you have a specific metal in mind, find the Lorentz-Drude model for the refractive index and add that as a dispersive material and terminate the waveguide with an object made of this material.
Scott