Temperture to index pertubation

I’m using the temperature profile obtained by heat device to perturb the index of refraction. I followed the steps explained in:
But it didn’t seem to work. As if the FDTD is not perturbing the index at all!
I have three question:
1-Is there any video/webinar explaining this specific procedure?
2-does Lumerical have a database of dn/dT?
3- Can you please check my attached file? because it is not taking the temperature profile.
Thank you in advance,
test.fsp (7.0 MB)

Hi @abeer.al-mohtar

Can you please watch this video and let me know if you are still having problem?


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Thanks for your reply. The video didn’t really help since it explains the same steps in the link https://kb.lumerical.com/en/ref_sim_obj_index_perturbation_material.html (that I followed without having successful results). Except for that the video is on charge transport that I am not using. (I’m using heat). can you please check whats wrong with my file because I first saved my temperature profile in heat. Then I added temperature as attribute. Then I imported the temperature profile. Then I added an index perturbed material with the material base that i need. then the simulation didn’t take this into account!!

Hi @abeer.al-mohtar

I did some search and you are right, unfortunately we don’t have a proper documentation on how you can do this. Here I will provide you with the steps and hopefully it would clarify the problem.

Lets say that you have exported the heat distribution data from heat solver. This is explained in this link. Also you have built the exact geometry in FDTD solver as Heat solver.

In FDTD, here are the steps that you need to follow to apply refractive index change with temperature:

First, define an index perturbed material from Materials tab and define how much refractive index will change with temperature. This is basically the material properties. For example, lets say that dn/dT=9e-5 for silicon at T=300k and at lambda=1.5um, where n is the refractive index and T is the temperature. We can have same argument for the imaginary part of refractive index (k) which I have assumed to be zero here with no loss of generality. Please see screenshot below for the steps:

I named the material to be called perturbed-silicon after defining it as new material, and set the parameters as above with base material selected to be silicon.

Advanced note:

If you expect to have a different value for dn/dT at different temperatures (dn/dT is a function of temperature), you can choose table of values instead of linear sensitivity.

Now, we need to add temperature profile of the geometry. From Attribute tab, choose Temperature, and name it to be temperature. Then from Edit tab select Import data and load the data that you have exported from Heat solver already.

Now that you have the temperature profile of your geometry and you know how it changes with refractive index, its time to let the software knows how to apply it into your simulation.

Select the structure, click Edit, and from the Material tab choose the material to be perturbed-silicon set grid attribute name to temperature as is shown below:

Now you selected the material which its index is supposed to change with heat and you have the heat profile at every position from temperature grid attribute. Software will automatically apply the modified refractive index based on the value for dn/dT and change in temperature imported from Heat solver: (n=n_silicon + dn/dT *ΔT).

You can add an index monitor and study how the material index changes at every position.

I hope this answered your question.


Thank you very much. Problem solved :slight_smile:

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