need `Material.get_n()`

[demisjohn]

For materials created with Material DB (not constant index), refractive index info should be returned when needed, acquired from FimmWave.

from Eric S: my old code used the function get_n() like this "Si.get_n()". Now this function does not exist in the Material class and I can't seem to find how this would actually be implemented with the Fimmwave command line. This Material.get_n() function should just return the index of the material that is initialized with a string of the material from the material database. I'm not really sure how to do this in Fimmwave besides using the Materials Inspector tool, but that seems to only generate a plot of the indices over a given wavelength range rather than return one index for the set wavelength.

[demisjohn]

Figured out a way:

When a slice's material is set, for example to Si3N4 in the matDB:

app.subnodes[1].subnodes[1].slices[2].layers[2].setMAT(Si3N4)

If the app.defaultlambda is set to the wavelength of interest, then when you convert that slice into a simple RIX-type material, like so:

app.subnodes[1].subnodes[1].slices[2].layers[2].setMAT()

FimmWave sets the slice's refractive index, which can be retrieved as so:

app.subnodes[1].subnodes[1].slices[2].layers[2].nr11
 >>> 2.1076151

You can then set the material back to it's original.

Works in the GUI - not sure if it works in the command-line

[demisjohn]

Looks like this doesn't work in the Command-Line - for some reason, changing the wavelength (either global or molab params for the WG) does Not result in the RIX (nr11) being updated when you switch the layer back to RIX-mode.

[demisjohn]

From Vincent Brulis: No command line version of the Materials Inspector.

If you want the refractive index one work around is to create a uniform waveguide containing the material and using the 3D Effective Index Solver to calculate the fundamental mode. If you set up the boundaries to give you a flat profile (a plane wave) then the effective index of the mode will be the refractive index. This also works for attenuation using the complex version of the solver; alpha will be given by modeLossEV.

[demisjohn]

Jared Bauters' method:

Jared's Material.get_n( ) function only worked for custom materials in the pyFIMM MatDB (by Including your own MatDB with your own material models in it), and also having a python module/function for that same material. So FimmWave gets the refractive index from the MatBD, while pyfimm/Python gets the RIx from the python function. It is up to the user to make sure that the MatDB/pyFIMM models match.

Since we already have a refractive-index module, adding these same materials to a custom matDB may not be too difficult.

I would only spend the time to code this up _IF_ WG.polish() (actually WG.calc(polish=True)) is significantly faster than rebuilding the WG with a new index & doing a fresh WG.calc(). This remains to be determined.