Learning Forum

[dubey]

As mentioned in this example there is two model for the graphene has been used. One for 1 ÅngströM and other for 7.5 Ångström thickness. I would like to know if it is possible to use different thickness of the graphene in simulation, if so, is there any change in the values ( e.g. fitting parameters for different ranges of Fermi level) must be made in order to that?

[dubey]

https://optics.ansys.com/hc/en-us/articles/360042243634-Electro-optical-modulator-based-on-a-graphene-coated-waveguide

[Guilin Sun]

The thickness is just a scale parameter when converting suface conductivity to permittivity. https://optics.ansys.com/hc/en-us/articles/360042244874-Graphene-surface-conductivity-material-model

So yes you can use other values for the thickness. The thickness does not change the Fermi level, but change the permittivity.

 

As you can see, for graphene, Lumerical provides two different types of material models, both are analytical. You can use either of them. You may need to compare with your experiment results and see which one is better for your device.

 

 

 

[dubey]

Hi, thank you very much for your reply.

I could not understand the last statement. Did you means inter and interband model (https://optics.ansys.com/hc/en-us/articles/360042244874-Graphene-surface-conductivity-material-model)? Do we have option menu to choose from material parameter in Lumerical?

Or did you mean  fermi energy model, for Ef ≤ 0.05 eV and Ef > 0.05 eV (https://optics.ansys.com/hc/en-us/articles/360042243634-Electro-optical-modulator-based-on-a-graphene-coated-waveguide)? In this case if we bias the device with both the positive and negative voltage  then we get both positive and negative value of fermi energy. Don't we have to use both model in this case?

 

 

[dubey]

Sorry, I meant to write fermi level*

[Guilin Sun]

Yes you can change the material parameters, including the fermi level. But you may need to know the relationship between the fermi level and applied voltage, which is not provided in the material model. You may need to find some papers for that.