Issue with Conformal Mesh Support in Tidy3D Mode Solver

[Guizhixing]

Hello,

I am currently trying to use Tidy3D's mode solver to compute the TEM mode field of a coaxial line.
I have been building my model with a relatively coarse mesh, but upon running the mode solver, I received the following warning:

“Mode field at frequency index 1, mode index 0 does not decay at the plane boundaries·······”

Additionally, I am unable to view the solver's data after this warning. I am curious if this issue is related to the conformal mesh support in Tidy3D, specifically whether Tidy3D supports PEC (Perfect Electric Conductor) with conformal meshing.

if there are recommended practices for setting up the model to avoid this issue, I would greatly appreciate your input.

Thank you for your assistance!

[momchil-flex]

It sounds like the mode solver is not getting the right mode. I have two questions:

• In your image, it looks to me like the PEC is not spanning the entire simulation domain, including the PML. If it isn't, you should definitely extend it fully so you get modes inside the cable rather than on the outer surfaces.
• In general, you shouldn't need PML here anyway (I don't know if you're applying them in the ModeSpec? or just in the underlying Simulation, which will not take effect in the ModeSolver).
• Also importantly, we do support conformal meshing for PEC, but only if you use our remote mode solver as e.g. mode_data = web.run(ModeSolver, task_name="coaxial). Using web.run specifically works in Tidy3D 2.8.0, in previous versions you need to import the separate mode solver run function from tidy3d.plugins.mode.web import run. If you do that, conformal meshing is turned on by default.

[Guizhixing]

@momchil-flex
Thank you for your response. Based on your suggestion, I modified the program and got an ERROR: “You do not have the permissions to perform this operation”. This suggests that it might be a software permissions issue.

[momchil-flex]

Sorry @Guizhixing did you ever resolve this yourself?

[Guizhixing]

@momchil-flex Yes, once I reactivated the permissions of Tidy3d, the program worked well. Thank you!