Is it possible to sweep sth only calculating the source mode?


Hey everyone!

I wondered if there’s a way in FDTD to sweep sth (in our case the thickness of a layer) and calculating only the mode and its properties (such as neff, loss etc) without running the whole simulation?



Hi @joe,

You can update the mode by using the “updatesourcemode” script command. You can get the effective index and mode profile using “getresult” as shown in the example of this command usage.

Getting the loss is a bit more tricky: although the mode selection tool show the losses polarisation fraction, there results are not provided, you would have to calculate them manually from the imaginary part of the effective index (this is shown here). Note that the mode source eigensolver uses metal boundary conditions as default. You may need to change them to PML to calculate lossy modes.
You can change the settings with the “seteigensolver” command.

That said, it would probably be easier to do such sweep using MODE Solutions instead of FDTD Solutions.