Mesh settings for shell waveguide


I am trying to do a simple simulation of a shell waveguide to find the guided modes and their effective indices, and I am having a hard time meshing the structure.

Since the majority of my waveguide is same material to the cladding, I have the mesh of my simulation region coarse and have a mesh override region just around the shell (as shown in mesh_1.png and ). But when I run the FDE simulator and click on “mesh structure”, I see the meshed structure as in meshedStructure_1.png. And I don’t know what to make of the black region around the shell?

I tried a different arrangement of mesh override regions where I place them at the corners of the waveguide so that their ‘+’ shape would cover the shell and extend outward a little so as to cover the interface between the two materials. (mesh_2.png and mesh_2_zoom.png), but “Mesh Structure” still gives similar black regions around the shell (meshedStructure_2.png).

What is the proper way to go about this?

Thank you very much

Looks like I was looking at the meshing result/index profile in the wrong window. When I do FDE -> data-> (right click on material) -> visualize -> index there are not dark regions that look like they haven’t been meshed.

I assume that your problem has been solved. If it isnt the case, please reply this post and I am happy to discuss that with you.