Why transmission larger than 1


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?

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:

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.


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