Reply To: Regarding Electric field on top of the waveguide

[Guilin Sun]

First, for the wavy feature, it might be related to source excitation which clips the mode field (please use log scale to check the mode profile), or the simulation span is short which cut the mode field profile.

Please increase the the lateral spans perpendicular to the propagation.

When the source profile is clipped it will cause diffraction.

When you plot the cut-line, make sure it is cut at the center of the profile.

You may try a smaller waveguide with shorter wavelength.

Ideally the mode should propagate very similar to theoretical prediction. Thus the problem is due to improper settings.