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mode analysis for 2D slab waveguide

Marvin Farrell
Hi, Everyone,

I am new for using comsol, and firstly I built a easy model to learn.
It is a 2D slab waveguide (see attached ).

By mode analysis, I found the effective mode index obtained by comsol is different with the value obtained by analytical solution.
In comsol mode, the infinite direction is set as PBC with continuity.

I appreciate you can give me some help.

Regards
Marvin


6 Replies Last Post Dec 26, 2016, 12:36 AM EST
Felipe Beltran-Mejia
Posted: 5 years ago Feb 21, 2013, 3:12 PM EST
you can be more specific.

what result are you getting? what were you expecting?

attaching the mph file also helps to help.

cheers,
Felipe BM
you can be more specific. what result are you getting? what were you expecting? attaching the mph file also helps to help. cheers, Felipe BM

Posted: 10 months ago Dec 9, 2016, 9:14 AM EST
Hi
I am also facing the same problem. I am using 2D slab waveguide with core 3.47 refractive index and cladding region is of 1.45 value. Comsol simulation shows smaller effective index value than what I have analytically calculated. I don't know why I am getting this smaller effective index value.
Thank you in advance.
Hi I am also facing the same problem. I am using 2D slab waveguide with core 3.47 refractive index and cladding region is of 1.45 value. Comsol simulation shows smaller effective index value than what I have analytically calculated. I don't know why I am getting this smaller effective index value. Thank you in advance.

Felipe Beltran-Mejia
Posted: 10 months ago Dec 9, 2016, 10:58 AM EST
Have you tried by increasing the resolution of your mesh?
Have you tried by increasing the resolution of your mesh?

Posted: 10 months ago Dec 10, 2016, 3:18 AM EST
Hello
Thanks for your reply. Yes, I have tried even smaller mesh size but I am not getting the expected result. I have tried different dimensions of my waveguide, different mesh sizes but unfortunately not getting the same value as I have obtained by analytical analysis.
Hello Thanks for your reply. Yes, I have tried even smaller mesh size but I am not getting the expected result. I have tried different dimensions of my waveguide, different mesh sizes but unfortunately not getting the same value as I have obtained by analytical analysis.

Nishit Malviya
Posted: 10 months ago Dec 16, 2016, 11:44 AM EST
Hi..

I think problem is that you have search for mode around value is lower than your lowest refractive index.

The value of search for mode around should be between the higher refractive index and lower refractive index.

Study>>>Mode analysis>>>Study setting>>>Search for mode around>>>>insert value 3.47.

Also, check mode analysis frequency>>>c_const/1550[nm] or direct frequency (Your operating Frequency or wavelength).

May it works.
Hi.. I think problem is that you have search for mode around value is lower than your lowest refractive index. The value of search for mode around should be between the higher refractive index and lower refractive index. Study>>>Mode analysis>>>Study setting>>>Search for mode around>>>>insert value 3.47. Also, check mode analysis frequency>>>c_const/1550[nm] or direct frequency (Your operating Frequency or wavelength). May it works.

Posted: 10 months ago Dec 26, 2016, 12:36 AM EST
Hello all
Yes I have entered refractive index value to be find as 3.47 and search for mode around option. Now I am concluded after all the experiments that when I am taking small dimensional waveguide it is showing effective index value near to 3.3 but when I am increasing my waveguide dimension its effective index starts decreasing. So may be our device dimension also play an important role in finding effective index value.
Hello all Yes I have entered refractive index value to be find as 3.47 and search for mode around option. Now I am concluded after all the experiments that when I am taking small dimensional waveguide it is showing effective index value near to 3.3 but when I am increasing my waveguide dimension its effective index starts decreasing. So may be our device dimension also play an important role in finding effective index value.

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