Learning Forum

[Han Wang]

Hello, community members.

I am a new user for Lumerical software, and I am learning how to use FDTD and MODE solutions to design and simulate photonic components, and I have two questions. 

1. In the example of Grating coupler, the goal is to design the TE grating coupler, but the fundamental TM mode is selected for the ports in the download example (please see blow figure). I would like to check the purpose and reason of setting this up.

 

 

2. In the example of Ring resonator getting started - Design and initial simulation, it shows the group index of 4.63 during the step of “Add eigenmode solver and find group index”. But I tried to simulate the same model and found the group index is about 4.8 in my simulation. I want to check whether it is because I use a new version of 2021 R1.2 and the example is based on one elderly version?

         

             Group index of 4.63 in the example                          Group index of 4.8 in my simulation

 Thank you for your help in advance.

[Afroditi Petropoulou]

Dear Han,
 
Concerning the first question you are probably right. I think fundamental TE mode should be selected in the mode selection. I will contact my colleagues to confirm that this is the case and if so, we will update the article. Thank you for bringing this to our attention.
 
For the second question when you do the frequency analysis you need to first select the mode from the list and then enable the "track selected mode" option so that the calculation will be performed for the specific mode for all frequencies.
 

 
Best Regards,
Afroditi

[Han Wang]

Hello, Afroditi. Thank you very much for your detailed answer and guidance! My problem is solved with your help.