Different response between 2D graphen and volumetric graphene

fdtd
fdtdsimulation
meshoverride
transmission

#1

Hello,
I am trying to reproduce the result from fig2 (a) from this:



In figure below big difference between 2 graphene modeling

It is clear that the result of volumetric graphene is so near to article result.what is the problem?
simulation file: Realization of Graphene-Based Tunable.fsp (603.8 KB)

Hope to receive your feedback.

Best Regards,
Dezyani


#2

Hi @m.dezyani
I read this paper from “link.springer.com” and i noticed that the schematic diagram of the structure is the following:

And the structure that you have build in FDTD is the following:

As you can see there is a difference in the structures. They are not the same .You have forgotten the left nanostructure in your design. Please, run the simulation with the left nanostructure.

I hope that it helps.


#3

Thanks for the reply.
I have a question:
Is the structure periodic when the boundary conditions use antisymmetric and symmetric?
I used this guidance:
https://kb.lumerical.com/en/ref_sim_obj_symmetric_anti-symmetric.html

Thank you so much.


#4

with periodic boundary conditions

(coarse mesh)
I think that boundary conditions is not my problem :neutral_face:


#5

In addition,this equation for graphene conductivity is reported at T=0 ,


#6

If is possible,please solve my problems.
Thank you for your kindly attention.

Dezyani


#7

Dear @m.dezyani

sorry for the wait.

Yes, when you set both boundary conditions (for example x-min and x-max) to symmetric or antisymmetric, it applies both symmetry and periodicity.

If you want to replicate the results of the paper, as @konslekk said, you need to change your geometry to be identical to the paper.

Can you please clarify your question? Is it because the simulation results for volumetric and 2D graphene don’t match?

Thanks


#8

Hi @bkhanaliloo

Do you see any difference between my simulation file and paper structure?

Thanks for your help.
Dezyani


#9

Dear @m.dezyani

The structure in simulated file is the same as the paper. The only parameter that I couldn’t find in the paper was scattering rate which might be the reason why transmission data don’t match with the paper!

The good is that I could reproduce some of the paper results such as the mode profile. Please see below:

As you can see in my simulation file : Realization of Graphene-Based Tunable-modified.fsp (257.2 KB)
I place monitors slightly below or above the center of the graphene as your mode along the z-direction is anti-symmetric and become zero right in the middle of graphene layer.

I also modified the mesh and find out that the results are sensitive to mesh along the z-direction. It looks like in your case, even if we are using a 2D graphene, we still need to use finer mesh along the z-direction as this KB example.

The bad is that, as I mentioned, the results for transmission is not as expected. First thing would be to do a sweep over scattering rate and see how it changes. Second, would be to change the Ef and reproduce the results of Fig.4 in the paper. Also, reducing the mesh size and conducting some convergence test would be a good idea to make sure that the current mesh sizes are good enough (I didn’t have time to go below the current size as simulations are taking more than one hour).

Please run the simulations and let me know if the problem has solved.

Have a good weekend :slight_smile:


#10

Hi @m.dezyani
Sorry for the delay. In the first file that you have uploaded "Realization of Graphene-Based Tunable.fsp " you have disabled the one of the three “2D Rectangles”. I mean that you should enable it in order to be the same with the paper.


#11

The transmission is:


The transmittance of dip is near to paper result.
I changed any parameter which has the influence on the result.

Best regards
Dezyani


#12

Hi,
I used this Scattering rate in surface conductivity of graphene for finding graphene scattering rate. I think this value is valid but still transmission spectra is not similar to paper result.


#13

Hi @m.dezyani

I guess I am not quite sure if the authors used the same scattering parameter in the paper. Were you able to change the scattering parameter and run the simulations for different values to see how the transmission plots change?

Thanks