# Which monitor to use to capture absorption spectra?

Hi,
I am try to measure absorption spectra for silicon in the mentioned
structure.can you help me what monitors are needed ?.

upconversion trail1.fsp (247 KB)

1 Like

Dear @fKorany

There are few ways to calculate the absorbed power, but maybe you can start with the simple method case:
https://kb.lumerical.com/en/index.html?layout_analysis_pabs_simple.html

The Pabs analysis group (open usr_absorption.fsp file) uses index and power monitor to calculate the absorbed power:

While your geometry is slightly complicated, refractive index and permittivity of the silicon is different than the rest of the material. Thus one approach might be to use conditional command such as if command to distinguish the silicon areas from other places or an script like below to integrate only over the silicon material:

################################################
# calculate power absorption
# as a function of x,y,z,f
epsilon = eps0*n_matrix^2;
Pabs_matrix = 0.5*W*E2_matrix*imag(epsilon)/SP;
Pabs_integrated = integrate2(Pabs_matrix,1:3,x,y,z);

####   new lines here
epsilon_silicon = epsilon*(imag(epsilon)==XX)        #replace XX with the imaginary part of the silicon permittivity
Pabs_matrix_silicon = 0.5*W*E2_matrix*imag(epsilon_silicon)/SP;
Pabs_integrated_silicon = integrate2(Pabs_matrix,1:3,x,y,z);

Thanks

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Thank you for help:blush:

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Dear @fKorany

I also find another easy way for you to find absorption on the material that you are interested at. A full description is provided in this page:

The idea is to use a an index filer that zeros absorbed power every where except the material of interest.

Thanks

Dear @bkhanaliloo ,
Thanks for help. I will try this method.
Thanks.

Dear @bkhanaliloo ,
This method calculates the absorbed power but i want to calculate the
absorption to calculate ultimate efficiency at the mentioned equation

Dear @fKorany

I donâ€™t know what exactly these parameters are, but I think you should be able to integrate absoption over the wavelength. Please go ahead preparing your simulation file and scripts and I will be glad to be of a help.

Thanks

Dear @bkhanaliloo https://kx.lumerical.com/users/bkhanaliloo
This is my simulation file. After simulation , I obtained the attached
figures but i think that these results are wrong. Can you help me to
identify the problem.

upconversion-trail2.fsp (287 KB)

Dear @fKorany

Just had a quick look at your simulation. The first thing that pops up is using symmetries for a design that is not actually symmetric. The pyramid is not symmetric and you have ring that is not centred in the middle of simulation. Please modify it and give it another shot.

Thanks

Dear @bkhanaliloo https://kx.lumerical.com/users/bkhanaliloo
I modified this mistake but result are not logic.
Thanks

Dear @fKorany

1. What are these plots and how did you extract them?
2. Why they donâ€™t make sense and What do you expect to see? Please provide references.

and provide your modified simulation file?

Thank

Dear bkhanaliloo https://kx.lumerical.com/users/bkhanaliloo,
Thanks for your interest. The modified simulation file and structure which
i want to validate are attached.
The previous plots extracted from transmission and reflection monitors. I
need to calculate the absorption at silicon materiel.
Thanks.

oe-22-S1-A1.pdf (2 MB)

Modified simulation file.fsp (278 KB)

Dear @fKorany

Can you please clarify what the result will be? Which plot in the paper shows transmission and reflection?

Looking at your current geometry and comparing the paper, your FDTD region should enclose the geometry and match the â€śsolidâ€ť object in your simulation file. You also need to modify the ring location.

Running simulations, I am not seeing any problem regarding the simulation itself. But I am hoping that you can build a geometry identical to the paper, and clarify what results we are looking for.

Thanks