Modal reflection (back reflection) of tilted ridge waveguide



Dear Lumerical community,
I have few questions about my simulation. I am FDTD to simulate a single mode passive tilted ridge waveguide structure ( of laser) to calculate modal reflection at different angles.
1 - In my simulation I am getting a lowest modal reflection, attaached grapgh, for a ‘straight’ RWG which is not true. Can anyone please help me to figure out where is the problem in simulation?

I have attached the the following files:
main() script file: angle_vs_reflection.lsf
geometry script file: tilted_facet2.lsf
graph: angle_vs_reflection.jpg


Hi @nouman.zia

It looks like your post is missing the files. Please also elaborate what you expect to see for the results.



Hi @bkhanaliloo,
I have now improved my deisgn and attached a script file tilted_facet_3.lsf (8.5 KB)
. I am interested to study the back coupling (reflection) of light from slab to ridge waveguide. I believe to see a decrease in the reflection with the length of slab waveguide (SWG) mostly due to absorption or then some coupling loss. You can see that I have placed a mode source in SWG and observing the reflection in RWG. I have attached a reflection plot for this configuration. I suppose that reflection should decrease here with the slab length.

On the other hand, when I place the mode source in RWG then reflection increases witth slab length, which is not true, I guess.


Hi @bkhanaliloo,
‘theta’ variable in line 21 is 7…


Hi @nouman.zia

It looks like you are discussing the case with my colleague @gbaethge in the post below:
Simulation tool and geometry

You can continue your discussion there. Please advise me if you have any concerns.