Discussion Forum

Hi,
maybe you should take a look to the pdf I uploaded in this discussion.

www. comsol.com/community/forums/rf-module/thread/31610

hope this can help

Adriano

Thank very much. actually I had downloaded this pdf already. Hope to implement it correctly.

To get the absorption cross-section define an integration coupling of volume type and select the domain of your nanoparticle, name it intV, for example. Then, under Model>Definitions, define your absorption cross-section as intV(emw.Qrh)/I0, where I0 is the intensity of your incident wave and Qrh the resistive heating.

In order to obtain the scattering cross-section define a surface integration coupling and select a surface that encompasses your nanoparticle, call it intS, for example. Then, under Model>Definitions, define your scattering cross-section as intS(dPsc)/I0, where I0 is again the intensity of your incident wave and dPsc is the scattering power you want to integrate over the surface. You can define dPsc as 1/2*Re{Esc x Hsc*}, where Re means real part, x is the cross product and * denotes complex-conjugate. To obtain the scattered fields, substract the background field from the total fiield (Esc=E-Eb).

Another way of calculating the absorption cross-section is through the same surface integration coupling but integrating the absorption power (-1/2*Re{E x H*}).

The extinction cross-section is just the sum of the other two.

Hope this helps in some way.. I'm currently working on doing this kind of simulations so If you need any other clarification feel free to ask.

Hello guys,

I have a graphene layer set as either a transition boundary condition (either setting the equation to dielectric losses or relative permittivity equation because I want to use its relative permitivity) at the boundary of two contacting Air blocks
(/or as a domain, which am not sure if it works since it is only 0.33nm too small).

This graphene layer is having PML blocks at its Width sides, but a Floquet periodicity at its other two Length sides to make it infinite at x-direction of its length.

I am using ports instead of scattetiring field condition, above and below the blocks of air. Graphene is in the middle and planar light (x-polarised) is meant to pass through.

The aim is to see what absorption is produced in the graphene but am not sure how to do this.

Most of people here use scattering field. Ports though give me a way to do Global evaluation for finding parameters S11, S21 and check the power of light reflected or transmitted.

Can you help me out?

I am able to show you pictures of what I have done until now!

Dear Yggdrasil


thanks for information, but do you mean if i want to simulate a silicon wave guide scattering (interaction between [pump/optical] wave with acoustic wave to generate a Stoke wave) i should use the background field as a pump and the port as stoke ?



Best regards

Hello,

I have some problems when making the model. I have a split ring resonator on the Si substrate. A beam of light is incident vertically on the ring. I use the ports and want to calculate parameters S11^2 and S21^2.

To the substrate ,the electric displacement field model should be relative permittivity or refractive index? In the port mode settings, I set E0x=1 and other two components are zero. The propagation constant is k0. I use wavelength of parameter sweep.

The result is that S11^2 has the lowest point and the S21^2 has the highest point. It is contrary to the theory. I can't find out the problem.

Hope you can help me!

Dear run


if you can attach your model, may be i can help you.



Best regards

When I attach file ,it points out that file size error. After I compress the file, it is still the problem. Is there other way to attach my model?

Thank you very much.

please delet the results and save it then you will find out that the size is ok.


Best

I have done as you say, but it still fail to attach.

Hi


delete the mesh


Best

I delet the mesh,the ports and down size of the model. It fails all the same. So I attach the sketch map.

Thank you!

I delet the mesh,the ports and down size of the model, but it fails all the same.So I attach the sketch map.

Thank you !

hi


please check the ports types: Rectangular, numeric ....



Best

I am not very clear with your suggestion.In the ports setting, I set the input quantity is electric field and E0x=1,E0y=E0z=0,propagation constant is k0. What's the PML used for? I don't set this in my model.

Put it on dropbox and paste the link!

Hi ,Yggdrasil,
I am a graduate student ,Tongji Unversity ,China. Now I use comsol to simulate some optical absorption. I saw your advice in Comsol forum and I sussceed calculating the absorption in the special eara. Next, I want to analysis the mode,but I don't know how to do it . I remeber the dispersion curve is useful.
You are good at comsol. Could you give me some advice?

Best regards,

Zhou Jian