Learning Forum

[vildemjo]

Hi,

I am trying to use a script I downloaded from lumerical's webpages which uses the advanced absorption (Pabs) monitor analysis group to plot the absorption in different particles (with different materials). Because I have a small mesh I had to limit the range in the global monitor properties compared to the source (I kept the source limits the same, so that the refractive index fit is the same as my other simulations). If I didn't limit the range the simulation took to much memory or had to low resolution in frequency.

My problem is that it seems like the fit to the refractive index is different in the monitors from what is shown in material explorer (see figure).

[Guilin Sun]

getfdtdundex is the material fitting data, and the index monitor may have two sets of results: before simulation and after simulation. Before simulation it is mostly used to check if the structure is correct. What is actually used in simulation is the result after simulation. Depending on where you place this index monitor, the result may have some difference due to conformal meshing. If you still have questions, please give more details on your settings so I can check.
To avoid script error, you only need to check the refractive index at a specific wavelength, no need to check at every wavelength since this is only a judgement to determine the material.

[vildemjo]

Okay, thank you. I ended up using the refractive index from a point in space where I knew what the material should be to find the material. Will the conformal meshing change the refractive index that much (the figure I added)? I thought it more likely that the fit used is different than the fit shown in material explorer. In my experience the fit can change a lot with the frequency range, but I didn't know it changes that much with conformal meshing.

[Guilin Sun]

You mentioned that you kept the same source spectrum range so the fit will use the source bandwidth. The global monitor settings should not affect the material fitting. Your point monitor should be placed inside the material so the conformal meshing will not affect the refractive index. Make sure you use the same simulation file, after the simulation for comparison. Internally, it uses convolution to realize the dispersive material, so the actual refractive index may have minor difference from the fitting. But it should not be that large. You should use the simulated refractive index or instead of in preview.