Learning Forum

[liyaqian]

I am trying to simulate an edge coupler assisted by multilayer SiN and SiO2 structure.When the mode overlap efficiency is only 40% simulated by FDE, the efficiency simulated by EME reaches 80%. I am confused whether 80% is credible. I think in EME simulation, the source port1 is placed in the fiber rather than the facet of the edge coupler, and port2 is placed over the output waveguide. So the result by EME simulation is the total efficiency. But how to understand the relationship between 40% and 80%? I think the result of FDE should larger than that of EME, which is contrary to the result in my simulation. Look forward to your reply. Thank you a lot.

[Guilin Sun]

I can only guess both "40% and 80%" are not correct:
overlap is an esitmation. It can be larger or smaller than the actual, physical coupling coefficient.

For EME, I am not sure how many number of modes you used and what is the structure of the waveguide. We have an online example: https://optics.ansys.com/hc/en-us/articles/360042305354-Edge-coupler

You may need to do converge test, with sufficient cells and mode numbers. Of course, if there is no strucutre change, only one cell is sufficient.