Learning Forum

[Z.Shahrabifarahani]

Hi everyone,
I try to plot the mode profile by the data I got from my lumerical data.
But the intensity distributation is going beyound 1.

Is it normal?  Because I was expecting to get the value which is normalized

[Dev]

Hello, this seems not right.

Can you share more details on how you extratcted mode profile.

Also, plot the same graph using lumerical and let me know.

Thank you.

[Z.Shahrabifarahani]

Hi, thank you very much for your prompt reply!

This is the script I used to get the data for my monitor:

monitor_name="1";

x=getdata(monitor_name,"x");

y=getdata(monitor_name,"y");

Ex=getdata(monitor_name,"Ex");

Ey=getdata(monitor_name,"Ey");

Ez=getdata(monitor_name,"Ez");

filename="Monitor_1";

matlabsave(filename,x,y,Ex,Ey,Ez);


And this is my matlab code to get this plot:

m =((numel(MyData.x)+1)/2) + 1;
   
   figure(i+1)
   grid on
   hold on
    
    m = ((x+1) /2) + 1;       #To get the central value of x which is the center of my stucture

   E_x = Ex(m,:,1,3);      # Ex(x,y,z,freq num)
   E_x_abs = abs(E_x);
   plot(x, E_x_abs,':', 'LineWidth',3)
  
   grid on
   hold on

   E_y = Ey(m,:,1,3);
   E_y_abs = abs(E_y);
   plot(x, E_y_abs,':','LineWidth',3)
   
   grid on
   hold on

   E_z = Ez(m,:,1,3);
   E_z_abs = abs(E_z);
   plot(x, E_z_abs,'b','LineWidth',3)
   

[Dev]

 

Thank you for sharing the code.

Which software you are using? I mean Mode or FDTD to generate mode profile? Which monitor are you using to generate mode profile?

Have you tried visualizing mode data in Lumerical software.

eg: I am using Eigen solver to generate mode profile of waveguide.

You can refer the following to extract the data: using getdata to grab mode profiles (ansys.com)

Thank you

 

 

[Z.Shahrabifarahani]

I am using FDTD solwer.
The monitor I am using is: DFTMonitor

And, yes!
When I visualize the E_y at monitor it's also the same as follows:

[Z.Shahrabifarahani]

But I need to explain that I am using a lot of DFTMonitors is a single simulation with distance of a 0.5 um and 1 um to get the mode profile at different spaces of my structure. 

I was wondering maybe too many monitors in a single simulation is generatig this error!
Here is my waveguide structure (an optical nanofiber with a polygonal cut throuth it).

 

 

[Z.Shahrabifarahani]

 

Just so you know, i ran my simulation and only kept one of monitors (and disabled the rest).
Byt infortunately I got the same problem. Here is the result I got from a single monitor in the simulation:

 

[Dev]

 

Hello,

DFT monitor records data for specified wavelength. The data is a mixture of all modes that were excited during the propagation. So the monitor might not be a good way to get the result.

I would suggest to usemode source and mode expansion monitor to get mode profile and S parameter or a or b coefficient to calculate mode amplitude.

Note 1 : If there is propagation and waveguide changes, the field profile is not a single mode. mode expansion monitor or port should be used to decompose the monitor data 

Note 2: FDE also produce nomalized results if cross section of waveguide is uniform. But in your simulation its not the case.

Hope this helps.

 

 

[Z.Shahrabifarahani]

Thanks for the explnation.

 

[Z.Shahrabifarahani]

But using the FDE solver is NOT a suitable solver for my case, as based on the explanation in your website, the cross-section of the waveguide should remain uniform, which is not the case in my simulation.

[Dev]

Yes. You are right. 

So the possible solution will be "using mode source and mode expansion monitor to get mode profile and S parameter or a or b coefficient to calculate mode amplitude".

 

[Z.Shahrabifarahani]

Great, Thanks!
I am currently using mode source, but I will try mode expansion from now on.