Impact of boundary conditions on bandstructure simulations
When simulating the bandstructure of a two-dimensional freestanding photonic crystal with a 3D FDTD simulation region, one can always make use of the symmetry of the problem to speed up the process. Initially, I was using the "Symmetric" option for both "z min" and "z max" boundary conditions, obtaining good-looking bandstructures. However, I read one should always set one of them to symmetric and the other to PML. This scrambles my bandstructures. Furthermore, if I want to include a substrate my structure is not symmetric anymore and I have to enforce PML boundary conditions for both "z min" and "z max". Also in this case, the bandstructure doesn't look clean. Could it be I am missing some key point one has to pay attention to when using PML boundary conditions?
Thanks in advance,