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R/T coefficients of two gratings

Posted May 10, 2012, 8:36 p.m. EDT RF & Microwave Engineering Version 4.2a 8 Replies

Hongtao Zhang
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Hello All,


I am calculating one model including two parallel gratings. I want to calculate the transmission and reflection coefficients of two gratings. The incident angle of the light α can vary from 0 to pi/2.

Different from the model of "Plasmonic Wire Grating", where they use S-parameters and “port”, I used a scattering field and PMLs. I attached the codes and a short explaination.


I am so confused by this calculation.


In addition, I tried to use port to calculate the R/T coefficients. But I always find some unnecessary oscilations in the curve. So I have to quit and use the above method. Is there any successful example of calculate the R/T coefficients for three or more layers media?


Thanks for your time!

8 Replies Last Post Jul 15, 2012, 2:34 p.m. EDT
Hongtao Zhang
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Posted: 1 decade ago May 10, 2012, 8:39 p.m. EDT
forget one thing: the code is in 4.2.a.
forget one thing: the code is in 4.2.a.
Alexander Kuznetsov
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Posted: 1 decade ago May 11, 2012, 12:49 p.m. EDT
You should model your grating with ports, not PMLs (as it's done in "plasmonic grating" example). PMLs+scattering BCs are trickier to setup.


You should model your grating with ports, not PMLs (as it's done in "plasmonic grating" example). PMLs+scattering BCs are trickier to setup.
Hongtao Zhang
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Posted: 1 decade ago May 11, 2012, 4:17 p.m. EDT
Kuznetsov, thanks for your suggestions.

In fact, I first followed the example and used the "port", I found one problem: oscillation in the R/T curve. Someone told me that there could be attributed to multi reflections at the port and some surface(s) of grating. i.e. the back and forth reflection between the port and some surface of the grating.


So I consider using PML to absore the wave to remove multi reflections.

Do you have some examples of R/T coefficients for multi-layer?

Thanks for your help.

Hongtao
Kuznetsov, thanks for your suggestions. In fact, I first followed the example and used the "port", I found one problem: oscillation in the R/T curve. Someone told me that there could be attributed to multi reflections at the port and some surface(s) of grating. i.e. the back and forth reflection between the port and some surface of the grating. So I consider using PML to absore the wave to remove multi reflections. Do you have some examples of R/T coefficients for multi-layer? Thanks for your help. Hongtao
Alexander Kuznetsov
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Posted: 1 decade ago May 14, 2012, 7:36 p.m. EDT
what do you mean by "oscillation in the R/T curve"? Are these the oscillations with angle of incidence, wavelength, etc.?
what do you mean by "oscillation in the R/T curve"? Are these the oscillations with angle of incidence, wavelength, etc.?
Hongtao Zhang
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Posted: 1 decade ago May 15, 2012, 3:18 p.m. EDT
Hello Alexander,

I upload one pic on my calculation. It polted the relation btw the R/T coefficients with incident angle. I attempeted to change the size of the mesh and these oscillation still exists.


It is the oscillation that caused me to use the PML+scattering field to calculate the R/T coefficients of the grating, not "Port".

Hello Alexander, I upload one pic on my calculation. It polted the relation btw the R/T coefficients with incident angle. I attempeted to change the size of the mesh and these oscillation still exists. It is the oscillation that caused me to use the PML+scattering field to calculate the R/T coefficients of the grating, not "Port".

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Alexander Kuznetsov
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Posted: 1 decade ago May 16, 2012, 2:50 p.m. EDT

Hello Alexander,

I upload one pic on my calculation. It polted the relation btw the R/T coefficients with incident angle. I attempeted to change the size of the mesh and these oscillation still exists.


It is the oscillation that caused me to use the PML+scattering field to calculate the R/T coefficients of the grating, not "Port".


Are you sure they are coming from ports? Way to check it is to shift your port by quarter-wavelength further away from the grating and see if the results changes. If that's the case, then I suspect that you didn't setup ports correctly. By looking at your grating, ports should work just fine.
[QUOTE] Hello Alexander, I upload one pic on my calculation. It polted the relation btw the R/T coefficients with incident angle. I attempeted to change the size of the mesh and these oscillation still exists. It is the oscillation that caused me to use the PML+scattering field to calculate the R/T coefficients of the grating, not "Port". [/QUOTE] Are you sure they are coming from ports? Way to check it is to shift your port by quarter-wavelength further away from the grating and see if the results changes. If that's the case, then I suspect that you didn't setup ports correctly. By looking at your grating, ports should work just fine.
Hongtao Zhang
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Posted: 1 decade ago May 16, 2012, 3:57 p.m. EDT
Thanks for your suggestions. I will check the port. In fact, "Port" method is simpler than PML and no need to calcualte the outflow power.

Hongtao
Thanks for your suggestions. I will check the port. In fact, "Port" method is simpler than PML and no need to calcualte the outflow power. Hongtao
Hangqi Zhao
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Posted: 1 decade ago Jul 15, 2012, 2:34 p.m. EDT

Hello All,


I am calculating one model including two parallel gratings. I want to calculate the transmission and reflection coefficients of two gratings. The incident angle of the light α can vary from 0 to pi/2.

Different from the model of "Plasmonic Wire Grating", where they use S-parameters and “port”, I used a scattering field and PMLs. I attached the codes and a short explaination.


I am so confused by this calculation.


In addition, I tried to use port to calculate the R/T coefficients. But I always find some unnecessary oscilations in the curve. So I have to quit and use the above method. Is there any successful example of calculate the R/T coefficients for three or more layers media?


Thanks for your time!


Hello, have you solved the problem? I have met the same problem when calculating the reflection and transmission coefficient in a similar model with you. I use ports firstly but there are also oscillations,and I don't know how to use Scattering BC +PML. Attached file is the model I'm following and it may help you. If you have any ideas please let me know, thank you.
[QUOTE] Hello All, I am calculating one model including two parallel gratings. I want to calculate the transmission and reflection coefficients of two gratings. The incident angle of the light α can vary from 0 to pi/2. Different from the model of "Plasmonic Wire Grating", where they use S-parameters and “port”, I used a scattering field and PMLs. I attached the codes and a short explaination. I am so confused by this calculation. In addition, I tried to use port to calculate the R/T coefficients. But I always find some unnecessary oscilations in the curve. So I have to quit and use the above method. Is there any successful example of calculate the R/T coefficients for three or more layers media? Thanks for your time! [/QUOTE] Hello, have you solved the problem? I have met the same problem when calculating the reflection and transmission coefficient in a similar model with you. I use ports firstly but there are also oscillations,and I don't know how to use Scattering BC +PML. Attached file is the model I'm following and it may help you. If you have any ideas please let me know, thank you.

Attachments:

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