Here I have thin layers in WG and under WG region, both of them are of thickness=300nm. I have to use dz=0.03um as an override mesh over their region. Apart from this, if I set the mesh in a couple gap only, nonuniform mesh with accuracy=1, the WG crossing PML boundary at the end will have mesh size = (dx, dy) = (0.072,0.072)um, which has little difference to that of previous override mesh.
Do you mean to set Y min/max as the steep angle PML? where it should be set nearly parallel to the light propagation.
Is it just for checking the divergence to move the PML right end to the center of the couple region? Is the result related to the splitting ratio of the whole device?
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