design direction coupling for add-drop ring

Hello Everyone,
I am going to design the coupling between bus waveguide and ring resonator. The widths of the bus waveguide and the bended waveguide is the same. There is a introduction about the directional coupler for identical waveguides. But for one straight, the other bended, does anybody know how to simulate the coupling efficiency for such structure by mode solution? Looking forward to get your help.

Hi, !

Actually, there is information on coupling between straight a waveguide and a ring resonator here:

Does it answer to your question?

Since you would like to consider the effect of the bend, EME is not preferable here. 3D FDTD is more convenient here.

Thanks. but I figured out the 3D FDTD is too time and memory consuming for such a large structure in my casee in which the bend radius is over 300 micros.

Thanks. Iit seems not very suitable for my case. One waveguide is straight, the other is a bended waveguide. I am thinking to use 2.5D FDTD.


I guess varFDTD is a good idea. Maybe you can prepare your simulation and share it with us?

I also thought that these links will be of interest for you to read:

Please let me know if you had further questions and I am happy to be of help.

Re-opening up this post since it relates to my query that i posted a few days ago. Very similar situation. Need to model a coupler with one straight and one bent waveguide with bend raidus > 5mm. Would be helpful to know the best solver option.

Best regards

Hi @sxd

I would recommend to use FDTD as it is more precise and should be quick for small radii. Please visit the link below for a similar example:

@bkhanaliloo: Thank you very much for the suggestion. Will have a look. Where can I find the simulation files? Unable to locate any download link on the webpage…

Hi @sxd

To get the files, you need to download the latest version of FDTD. Then you can select the application of interest from the “welcome” window. Please watch the video in the link below for more details:
New Applications Gallery available in Lumerical tools