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Ansys Learning Forum › Forums › Discuss Simulation › Photonics › MODE: Strange mode result from FDE solver › Reply To: MODE: Strange mode result from FDE solver

June 4, 2024 at 11:44 am
Henrick Höllerer
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Hello Amrita,

thank you very much for your help.
I now tried both of your suggestions, setting n=2.18 and using fewer mesh cells for the background mesh. 
Unfortunately, the error still occurs but interestingly only when I execute the code for the first time (e.g. after restarting MODE):

The effective indices of the found “false modes” are then equal to the effective index I set in the modal analysis tab. I re-run the (exactly same) simulation 20 times and only observed the error for the first run - which is at least significantly less than before. Moreover, I repeated the sweep of the waveguide top width with the new settings and run the code on a different computational server of my university, too. In both cases I made again the observation: for the first time running the simulation the strange mode result occurred.

Best regards,
Henrick