# the question about the bent waveguide example

#1

dear all
I have learnt the bent waveguide on your website.

however I can’t get the same answer although I do as you teach us.I can’t get the right mode when I can check the “bent waveguide” option, and calculate the mode in the bent section of the waveguide,which as show below.

I dont know how to make it right and get the right result as you show.

second question: on your website,you said that the overlap calculated between the two modes is about 98.8% while the value on the picture you show is just 99.78%(as the picture show above).What I want to know is that which answer is right.

Can anyone help me solve the two questions? Hope to get yourfeedback. Thanks a lot.

#2

The reasons are likely that: 1) you are using an older version of MODE. 2) You changed the boundaries, FDE dimensions or the mesh.

#3

I am learning the bent waveguide, too. The xy plane is actually the cross-section of the waveguide. It can be set easily in the interface. My question is how to set the bend of the waveguide with the structures in Lumerical?

It seems that the bend is set by click the ‘bent waveguide’ box in the modal analysis. For some complex structure, how to set the bend? Thanks.

#4

For example, I’d like to simulate a s bend waveguide. In the object library, there is the bend waveguide that I can use to build the structure in the horizontal plan. But in this way, it seems difficult to define the cross section of the waveguide.

Sincerely,

Quentin

#5

Dear @quentinl,

The bent waveguide analysis that is discussed in this topic is offered by the FDE solver in MODE and is capable of simple bend structure with single radius of curvature and bend orientation. For an S-bend, you cann’t use this analysis and you need to use FDTD or EME solver. Visiting the following topics can be helpful:

You can also find other related topics about s-bend in KX by searching for the s-bend keyword

#6

@mmahpeykar Thanks for your information. I will try it again later. If I have any questions during the process, please allow me to disturb you. Appreciate for you.

#7

@mmahpeykar Just ran my first model on silicon waveguide for a potential customer of Lumerical. Something weird is that I can’t see the loss of the s bend.

Maybe I need to read some published literatures on silicon waveguide, since not familiar with this research topic.

#8

You can create a new topic and provide the simulation file and a detailed description of the issues so that the community users can help.