How to set up the input file for calculating two-photon absorption

Questions and doubts about features of non linear optic in Yambo (yamb_nl)

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Zhengran Wu
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Joined: Tue Jul 27, 2021 9:06 am

How to set up the input file for calculating two-photon absorption

Post by Zhengran Wu » Fri Jul 30, 2021 9:34 am

Dear all,

Is YAMBO currently possible to calculate two-photon absorption (TPA) spectra?

I have seen several papers that have calculated TPA using Yambo (https://doi.org/10.1103/PhysRevB.98.165126, https://doi.org/10.1103/PhysRevB.96.245109). There is also a post-processing script (https://github.com/yambo-code/yambo-min ... tion_PP.py) that "extract two-photon absorption and intensity-dependent refractive index from ypp". So yambo is possible to calculate TPA?

If possible, how to set the parameters in the input file? I couldn't find any tutorials for calculating TPA in yambo or lumen. According to this NLAbsorption_PP.py, at least two field intensities are needed. But I don't know how to set. Also, since TPA is a third-order process, why does the NLAbsorption_PP.py script require input files of the first order("_order_1") instead of the third order?

Bests
Zhengran
Zhengran Wu
PhD student
Institute of Physics, Chinese Academy of Science

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claudio
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Re: How to set up the input file for calculating two-photon absorption

Post by claudio » Fri Sep 10, 2021 8:01 am

Dear Zhengran

sorry for the late reply.

Yes in principle it is possible to extract TPA with Yambo, even if it is rather complicated.

The procedure is described in
https://journals.aps.org/prb/abstract/1 ... .98.165126
in section III.A

In practise you choose and energy range you are interested in, for example between 1 and 2 ev,
than a number of frequencies you want in this range, for example 40 points.

Then you run a simulation with a sinusoidal field at a given intensity E, you repeat the calculation with intensity E/2 and E/4.

You subtract the different polarization using the formula Eq. 18 of https://journals.aps.org/prb/pdf/10.110 ... .98.165126
and the Fourier transform the result.

I will try to prepare a tutorial on this kind of calculations

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Zhengran Wu
Posts: 6
Joined: Tue Jul 27, 2021 9:06 am

Re: How to set up the input file for calculating two-photon absorption

Post by Zhengran Wu » Fri Sep 10, 2021 3:28 pm

Dear Claudio,

Thanks for your instruction! Now I generally understand the calculation procedure. I will try to extract the polarizations and do the Fourier transform. But I'm afraid it is not easy for a newbie like me.

It would be so great to see a tutorial on this.

Best,
Zhengran
Zhengran Wu
PhD student
Institute of Physics, Chinese Academy of Science

Zhengran Wu
Posts: 6
Joined: Tue Jul 27, 2021 9:06 am

Re: How to set up the input file for calculating two-photon absorption

Post by Zhengran Wu » Fri Oct 15, 2021 3:21 pm

Dear Claudio,

I figured out how to calculate TPA. Thank you very much for the previous tips.

I have one more related question: how to consider the effect of different polarizations of the E field on TPA? Since the calculation uses the intensity dependent first order susceptibility, I have no idea which tensor elements are non-zero. (I only know the non-zero elements of second/third order susceptibility)

Best,
Zhengran
Zhengran Wu
PhD student
Institute of Physics, Chinese Academy of Science

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claudio
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Re: How to set up the input file for calculating two-photon absorption

Post by claudio » Mon Oct 18, 2021 4:31 pm

Dear Zhengran

setting the polarization in input you can select the three components,
but I understand that if you want off-diagonal terms you need two fields.
We are adding a second external field to yambo, and we will release a new version soon.

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

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