Reply To: Checking neff in FDE mode solutions – 3D Model

[Guilin Sun]

There is no such neff for a 3D structure, except you consider it as a cavity. 

When you optimize the taper length, the cross section does not change for each cell. so it does not matter for the neff at each cross section.

Please note both EME and FDE gives neff for the waveguide mode at the waveguide cross section, which is always 2D or 1D, not 3D.

neff is associated with a mode. the mode properies of the taper are different at different cells along the taper. Not sure how do you associate 3D neff to a "mode"? if you can, it is an approximation. Please reconsider its physics. You may try to find some publications to get some information on what you want to get.