Evanescent waveguide couplers



I am new to Mode Solutions. I am trying to execute the “Evanescent waveguide coupler” for a fixed separation between the waveguides, without the script. These are the steps that I do:

  1. Calculate the mode of the first waveguide using FDE, and store the fundamental mode as a d-card.
  2. Introduce the 2nd waveguide and solve for the supermodes of the system.

3.HOW do I (now) launch the fundamental mode stored in the d-card (as a superposition of the supermodes) into the first waveguide and look at the propagation?

  1. I wish to simulate propagation in a fiber directional coupler. Can I use EME (varFDTD will not work for fibers) or do I have to use 3D FDTD?

Would sincerely appreciate some pointers.



Hi, @sxd !

Did you try this example: https://kb.lumerical.com/en/pic_passive_waveguide_couplers_evanescent.html ?
It is very instructive.


Thank you. Yes, that is where I started. But instead of using the script, I wanted to understand how to launch the single waveguide mode at the input while both the waveguides are present.



The methodology that comes to my mind first, is to divide the directional coupler into sections.
The first is for single waveguide input, which mode can be customely selected. The second one is the coupler itself with two waveguides, one of which is for input seed. This way you can model the coupler by EME and FDTD.

Both EME and FDTD should work all right for directinal coupler.


Sorry @msaygin
I was completely off grid this last one month. Thank you very much for the suggestion. Will try to execute it and get back. regards.