Learning Forum

[ph23resch01002]

Dear Sir/Madam,

I am generating structured light, such as a vortex beam, at the focal plane at a distance of 20 μm using a metasurface. I have the electric field profiles at the xy and xz planes and now want to analyze the polarization of the field at the focal plane. How should I go about this? While searching, I found that plotting the vector field on top of the contour plot of the electric field in the xy plane could be useful. I came across the quiver function in MATLAB for plotting the vector fields. After exporting the electric field data at the xy plane to MATLAB and using the quiver function, I did not obtain the expected results.

Can you please tell me how to determine the polarization of the field at the focal plane using Lumerical FDTD?

Thanks in advance.

[Guilin Sun]

This is a more theoretical question than simulation.

If such beam can be quantified in one plane, it might be on the focal plane. when light propagates along z, it is xy plane, then you can plot the vectorial field using visualizer:

 

those are just for visualizetion. if you can quantify the fields in math it would be better.

 

On the other hand, if it can only be quantified along the propagation direction, you can use a ling monitor along z and plot the vectorial fields.

Please note that, Matlab uses equi-spacing data whereas FDTD is graded mesh, non-uniform data. Before save it to matlab data please interpolate the data:

interp - Script command

[ph23resch01002]

Hi Sir,

I am following the metalens example provided on the Ansys Lumerical website to generate a vortex beam at the focal plane z = 20 μm. Using a DFT monitor at  Z = 20 μm to observe the vector fields would be computationally expensive. In the metalens example too, the far-field projection has been used to obtain the intensity profile. I would like to get an intensity profile with polarization as shown in the figure below.

 

Is there any other way to get the polarization plot other than using a line or field monitor at the focal plane?

Thank you,

Bharathy J

[Guilin Sun]

Sure you do not need to simulate from metalens to its focus plane. you can use a monitor to record fields behind the metalens, so the simulation region is small. then use farfieldexact to get the fields at the focal plane: https://optics.ansys.com/hc/en-us/articles/360034930733-farfieldexact3d-Script-command

then you can analyze the field vectorial property with the resulting Ex,Ey ans Ez, not directly from the monitor.

You will need to analyze the polarizarion property of the fields.