Learning Forum

[maori.cabanes]

Hello. I have a question about this article : https://optics.ansys.com/hc/en-us/articles/1500008021262-Optimizing-waveguide-geometry-for-single-mode"

It is said "The modes are only supported if the effective index of the mode is larger than the effective index of the slab mode of the slab waveguide". I assume "modes are supported" is a synonym for guided modes, right ?

I thought that a mode could be guided if its effective index was higher than the index of the cladding, is it right ? If so, what is the link with the effective index of the slab mode ?

[Guilin Sun]

The slab mode is from the 1D slice of the waveguide. It is not necessary here to introduce such 1D slab mode I believe.

I guess its meaning is, if you decople the 2D mode into 2 1D slab  modes, the first slab mode should have larger effective index than the 2D cross section of the real waveguide. the 2nd slab mode has about the same effective index as the 2D mode. such concept is used in VarFDTD: https://optics.ansys.com/hc/en-us/articles/360034917213-MODE-2-5D-varFDTD-solver-introduction