How to import mode source from other modesolver

[694856790]

Hello, I want to know whether MEEP can support external mode field import, because I found that MPB can not calculate the mode field of lossy media, so I want to obtain the mode field through other mode solver to use as the mode source, is there a good way? Thanks.

[smartalecH]

Sure if you have the mode field profile (eg computed with a different mode solver), you can inject that as a source. Here's a thread you can follow:

#2218 (comment)

@hammy4815 did you write up a tutorial that does this? @oskooi might be good to add this as a FAQ.

[694856790]

@hammy4815 Thanks! The mode source is a 2D image ( a 2D matrix), which I think should match your description. However, I am not very familiar with the pattern monitor. Can I load my own mode fields into the mode monitor to get the mode coefficient to calculate the S parameters?

[hammy4815]

Ah, if you want to calculate the mode coefficients using your provided mode patterns, you can just use get_dft_array to grab the field profile at a given frequency and manually compute the mode decomposition using overlap integrals (see here).

[694856790]

That's a good idea, thank you!

[694856790]

@hammy4815 By the way, I want to confirm, should I use a normal DFT monitor or a mode monitor to capture the profile of fields? The mode monitor should distinguish between energy forward transmission and backward transmission, is that right?

[hammy4815]

You should just use the DFT monitor if you want it to match your provided mode profiles, rather than those solved for by MPB. To distinguish between forward and backward propagating modes, you need both profiles to compute their respective overlaps.