Why transmission larger than 1

Hi

I am trying to figure out if my structure has a bandgap so I monitor the transmission at the edge of the structure but it has a transmission larger than 1. can someone help me with this?

Best,
Zhou
cavity.fsp (532.9 KB)

Dear @iambud

Thank you for sharing simulation file.

Since you are using a mode source that injects light in the x-direction and thus breaks the symmetry, you can not use any symmetry along x. Also I recommend you to move the mode source before the gratings, start with standard PML and increase the number of layers, and use slightly finer mesh along the x to resolve gratings properly. Here is a good reference to learn more about convergence testing:
https://kb.lumerical.com/en/index.html?layout_analysis_test_convergence_fdtd.html

Here are a few other reasons that may cause transmissions above 1:
Transmission higher than 1
Transmission of a structure over 1

I hope this solves the problem.

Sry I just forget to reply… ye It helped me to solve the problem, thank you very much.

Best,
Zhou

1 Like