Photonics

Photonics

Topics related to Lumerical and more.

Autoshotoff problem during band structure analysis

    • Pouya_Panahianfar
      Subscriber

      Hello,

      I'm trying to perform a 2D FDTD simulation with my own defined material in order to find band structures of a Photonic Crystal. This is how main simulation looks:

    • Guilin Sun
      Ansys Employee
      The fitting has no series issue, since the imaginary part is almost a constant. However, you may not need to use such a small weight.
      What is the actual simulation bandwidth in the dipole clod?
      if they do not match, please view the material fitting in this simulation range.

      It seems there is something wrong for the autoshutoff level, probably diverged. Please check the log file.


    • Pouya_Panahianfar
      Subscriber
      Hello dear gsun Thanks for your reply. As you mentioned, I lowered imaginary weight and therefore here are new plots:
      Also simulation bandwidth in dipole cloud is set as a parameter in model script. Which in my case it is same as shown in material fitting window. To be exact, f1 = 20 (THz) and f2 = 400 (THz). However I tried your suggested range and the issue still remains. I changed fit range to make it as fit as possible. Here is the result for you to see:
      I also checked the log file and there seems to be a problem!
      Here is a part of log file which I think is the key:
      Starting meshing
      Simulation size in gridpoints: 95 x 95 x 1
      Refined 0 mesh cells (0%)
      Completed meshing!
      Meshing complete in 0.015625 seconds of CPU time
      Numerical discretization of material 'mat_test' might be unstable! Max. imaginary part of epsilon is 35.6173!
      64496 64496
      Selected kernel with optimization level: 2 and split-field propagation direction: 0
      I would really appreciate your help to fix this problem.
      Thanks again!
    • Guilin Sun
      Ansys Employee
      Is this material data from nature or artificially engineered? It says it is the material issue. Please check your wall message.
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