# Can I define chi3 as a function of electric field in x,y direction (FDTD)?

#1

hi,
I have a big problem.
I wana use chi3(3rd order nonlinearity) as a function of electric field in x,y direction(E(x,y)), how can I do this?
for example: chi3= 5.6*(10^-11)*E(2,3)
E(2,3) is not constant and changing during the simulation.
thanks

how can I implement a material plugin in FDTD Solutions?
#2

This is one line from the current chi3.cpp

return V/(U+chi1[axis]+chi2[axis]*E+chi3[axis]EE);

I think it is possible to make it

return V/(U+chi1[axis]+chi2[axis]E+chi3[axis]EEE);

Do you think it can simulate the effect you have in mind?

By the way, what kind of application you are trying to simulate? If you can find a reference how this effect can be simulated using an FDTD method, it will make things a lot easier.

#3

thank you so much
but I have a question, how can I do after change this code?

#4

hi,
I have a big problem, I wana change the chi3 code (chi3.cpp) and use it, how can I use it? should I write this code in the script? or save this code in the windows’s drives?
help me
thank you
https://kb.lumerical.com/en/chi3.cpp

#5

It looks like your new question is related to this post and therefore I moved it to here for a smoother conversation.

To make a new plugin (or modify), you will need C++ to compile the new plugin material, for more information please refer to this page and watch a practical demo video how this can be done.

A bigger questions to me is that what application you are trying to simulate. By making the modification I suggested, I think chi3 will effectively become chi4. So I am still not 100% convinced that why you would want to do that, unless you really want to simulate the effect due to chi4.

#6

absolutely
I wana use chi4 effects.
I went to that page but I didn’t find any thing about C++.

#7

There should be a link named “Material Plugins: A Practical Implementation Demo”, that will take you to watch a demo video how to generate the new .dll file.

What kind of application you are trying to simulate? I can try to suggest something we might already have for you to get used to the software before trying on your new chi4 model.