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Hello Minoo Kabir

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Hi Minoo,

I have done some thing like following (2D square Lattice, solid cylinder in solid matrix),but I did not get the z-mode (longitudinal mode), just the transverse mode only:
1. used acoustic-structure interaction, elastic wave (elw) module
2. chose both domain linear elastic material.
3. Floquet periodicity (1,4) and (2,3) boundaries.
4. took the parametric sweep for kx = 0 to pi/a .
5. finally got kx vs freq (derived values > global evaluation),

but this kx vs freq gave me just transverse modes only, longitudinal mode missing.

BTW did you figure it out how to do it properly ?

Thanks

Hi, have you figured out the problem of calculating the bandgap of photonic crystals? I'm also encountering some problems when studying the case of Optical waves "bandgap_photonic_crystal.mph." About the case, I have some questions:
1. the corresponding PDF of bandgap_photonic_crystal.mph says that the refractive index of GaAs is frequency dependent, and the setting of "wave equation, electric 2" gives n_GaAs(freq1), while "freq1" has the dimension of intensity of electric field V^2/m^2, could you explain this?
2. In the sixth page of "WaveOpticsModelLibraryManual.pdf", figure 4 gives the band diagram for k swept from 0 to 0.5 in the (1,1) direction. But i cannot find the corresponding settings standing for the (1,1) direction in bandgap_photonic_crystal.mph. could you tell me where the corresponding settings standing for the (1,1) direction in bandgap_photonic_crystal.mph are? or could you tell me how to figure out the whole band diagram of photonic crystal including Gamma--M--K--Gamma, just like the band diagram given by Rsoft?
3. could you briefly tell me the process of calculating band diagram and equifrequency surface of PhC using Comsol Multiphysics?

If possible, please send the message to "hujinbing@usst.edu.cn".

best regards

Jinbing Hu

hi

i want to know if you could help me to calculate the transmission curve for 1D phononic crystal ??

if you can help me, this is my e mail

nagatyphys@science.bsu.edu.eg

thank you

I uploaded a COMSOL file to the Model Exchange that shows how to set up a phononic band gap analysis in COMSOL. Here is the link: www.comsol.com/community/exchange/432/.

Nagi Elabbasi
Veryst Engineering

how can i control the filling fraction in the phononic crystal to know its effect on the band gap ??

Hi Nagi Elabbasi,
The model in the link (www.comsol.com/community/exchange/432/.) cannot be downloaded. I really need this model. It is very important to me. May you send an e-mail to me? My E-email address is wangchen_neuq@163.com
Best wishes,
Chen Wang

Ahmed, by filling fraction I assume you mean the size of the inner core material. That you control by changing the L2 variable.

Chen, I prefer if you download the model from the COMSOL site. Support should be able to help if download doesn’t work.

Nagi Elabbasi, thanks. I will send an e-mail to the support.
Best wishes,
Chen

Dear Elabbasi,

your square lattice phononic crystal model is help us to understanding the obtain band gap very much. Could you describe us to obtain band gap if we use the triangular lattice same way please? I mean which shape we must use as a unit cell for correct results?

Thank you.

Dear Nagi

really thank you very much i have calculated the band strcture of my system as in the attached figure ...

but i have a problem in the wave vector axis , i want it to take the coordinate (M X) of the first brillion zone ...

also i want to calculate the transmission ..

thank you

Hi, Nagi,

I am working on the bandgap analysis of photonic crystals with RF module and trying to reproduce the example 'Bandgap Analysis of a Photonic Crystal' in the COMSOL Application Library. I'm encountering several questions.
1. k1=1 and k2=1 mean the [1,1] direction, right? If I want to plot the whole dispersion relation including Gamma-K-M-Gamma, do I need to calculate [1,0], [0,1] and [1,1], seperately? Then make them in one plot?
2. I cannot really understand the sweeping of k , why is it from 0 to 0.5? why isn't it from 0 to 1?
Thanks in advance.

Best
Tianjing

Chen, I prefer if you download the model from the COMSOL site. Support should be able to help if download doesn’t work.

Hi Nagi Elabbasi,

I am having the same problem of what Chen has, I just started to use Comsol recently but since Chen's question, regarding the file is not available, was a year ago and still the file is not fixed, I assumed that I can contact you and ask you if you can personally re-upload it or send it to me ?

This simulation is very crucial in my research, so can you please help me with this problem ?

I really appreciate your help

Thank You

Regards,
Abdulrahman

Dear Abdulrahman, I prefer that you contact COMSOL to see why the download does not work. I just tried it and it works on my computer.

Dear Tianjing,

In the COMSOL model you refer to they sweep k from 0 to 0.5 because of the way the kx and ky vectors are defined: there is a factor of 2 in the b1x, b1y, b2x, b2y definitions. In our model we don’t have that factor so have to sweep over k from 0 to 1. Regarding your first question, yes you need to sweep the other 2 sides as well. You can do that in separate analyses or if you want to keep it all in one analysis use the “if” statement to define kx and ky, just like we did in our model.

Nagi Elabbasi
Veryst Engineering

Dear Abdulrahman, I prefer that you contact COMSOL to see why the download does not work. I just tried it and it works on my computer.

Dear Nagi Elabbasi

Thank you for your reply and I did contact them

The file size is supposedly to be ~20 MB but when I download it, it becomes 40 KB

so I can download it but the size is incorrect and when I open it, it gives this message

COMSOL Multiphysics model file is damaged or not valid.

I will check with comsol support regarding that

Thank You So Much For Your Help

Regards,
Abdulrahman

Dear Nagi,

Thanks for your reply. Now I understand about the definition of "k". I will try to use the "if" statement. But I still have one question about the bandgap analysis. I am trying to work from the 2D model to the 3D case because my structure has a substrate in the bottom. So it's periodic in x- and y- direction, but not in z direction and not infinite in z- direction.
I think it is still a 2D periodic photonic crystal, so I don't need to change the definition of a1, a2, b1 and b2 in my 3D model, right? I think COMSOL can work for 3D case, but my eigenfrequency is always complex, and I don't know why.

In addition, how to define nEz in 3D model. It is defined as intop1(realdot(emw2.Ez,emw2.Ez))/A in 2D model. Is there any example for the 3D case? I didn't find it. Thank you very much.

Best
Tianjing

Hi, Nagi,

I have one more question. For the example 'Bandgap Analysis of a Photonic Crystal' in the COMSOL Application Library, could you please explain why we need two studies to get the dispersion diagram? Is it because the refractive index of GaAs is frequency dependent? However, even if it is frequency dependent, we still can sweep the wave vector k in the eigenfrequency solver. Is this method correct? I tried, but got different dispersion diagram. I want to simplify this model because my structure is very complex.
Thanks in advance.

Best
Tianjing