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How to define the incident light area in Mode Analysis?

Posted 25 nov. 2014, 19:20 UTC−5 Electromagnetics, RF & Microwave Engineering, Structural & Acoustics 4 Replies

Huashun Wen
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Hi all,

I want to do mode analysis of a rib waveguide, as shown in attached figure (a). But the modes I got are not guided in the waveguide, as shown in attached figure (b).

I think the incident light area (or something like this) should be defined, so that the modes can be guided in the waveguide, as shown in attached figure (c). So question is how to define the incident light area, or how to set in Mode Analysis? So the modes will be guided in the waveguide. Thank you.

Best regards,

Huashun

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4 Replies Last Post 8 déc. 2014, 13:59 UTC−5
Felipe Beltran-Mejia
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Posted: 10 years ago 27 nov. 2014, 08:16 UTC−5
Dear Huashun,

My suggestions:

First, refine your mesh inside the rib.

Second, temporarily declare the upper Si region with a lower refractive index (for example air n=1). Same thing with the Si substrate.

Run your study computing for 6 modes and using the Si refractive index as the first shoot for the effective refractive index. Look for the computed effective refractive index of the computed mode, as it will be a good "second shoot" for the next step.

Reestablish the correct refractive index for the top layer and the substrate. Now use your "second shoot".

good luck!
Felipe Beltran-Mejia
Dear Huashun, My suggestions: First, refine your mesh inside the rib. Second, temporarily declare the upper Si region with a lower refractive index (for example air n=1). Same thing with the Si substrate. Run your study computing for 6 modes and using the Si refractive index as the first shoot for the effective refractive index. Look for the computed effective refractive index of the computed mode, as it will be a good "second shoot" for the next step. Reestablish the correct refractive index for the top layer and the substrate. Now use your "second shoot". good luck! Felipe Beltran-Mejia
Huashun Wen
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Posted: 10 years ago 1 déc. 2014, 13:57 UTC−5
Hi Felipe,

Thanks a lot for your suggestions, they are very helpful.

I'd like to ask another question, how to do the Mode Analysis which is only for the TE polarization light? Thank you.

Best regards,

Huashun Wen
Hi Felipe, Thanks a lot for your suggestions, they are very helpful. I'd like to ask another question, how to do the Mode Analysis which is only for the TE polarization light? Thank you. Best regards, Huashun Wen
Felipe Beltran-Mejia
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Posted: 10 years ago 1 déc. 2014, 14:03 UTC−5
Huashun,

I don't know if I really understand your question, but I'll give a shoot:

Compute for various modes. Locate your TE mode and copy the effective refractive index.
Compute again but just for one mode and using the effective refractive index as the value to search around for.

You should get only your TE mode. Now you can start working with it.
Also, if you want to modify any material or geometrical parameter, you shall do it in small steps so you can keep track of the TE mode effective refractive index.

I hope that helps,
Felipe Beltran-Mejia
Huashun, I don't know if I really understand your question, but I'll give a shoot: Compute for various modes. Locate your TE mode and copy the effective refractive index. Compute again but just for one mode and using the effective refractive index as the value to search around for. You should get only your TE mode. Now you can start working with it. Also, if you want to modify any material or geometrical parameter, you shall do it in small steps so you can keep track of the TE mode effective refractive index. I hope that helps, Felipe Beltran-Mejia
Huashun Wen
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Posted: 10 years ago 8 déc. 2014, 13:59 UTC−5
Hi Felipe,

Thanks a lot for answering my question.

My question is how to choose TE or TM for mode analysis, as described here www.comsol.com/community/forums/general/thread/7478

Hope you could help me. Thank you.

Best regards,

Huashun Wen
Hi Felipe, Thanks a lot for answering my question. My question is how to choose TE or TM for mode analysis, as described here http://www.comsol.com/community/forums/general/thread/7478 Hope you could help me. Thank you. Best regards, Huashun Wen

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