Ideal binary grating


in order to learn more about Lumerical FDTD, I’ve chosen a very simple example with an analytical solution: a binary square-wave grating.

Theory says that this kind of grating has only odd number transmission orders for normal illumination. So far, I think I have managed to do well and now I can see n=+/-1 orders. Also I have managed to do a surface plot in the way I need it:
image(th,f,Pz) # where th is the angle over the x-axis of the monitor, f is frequency and Pz is the z-component of the Poynting vector.

Now I want to do this same plot for the far-field. I cannot make it 2D, since later I plan to break the symmetry. Can you please tell me which commands I need to obtain a matrix such as Pz for the far-field?

At the end of this post, you can find attached my model along with the script I’m using to plot the results.

Thanks in advance.
graph_PUM.lsf (353 Bytes) square_diffraction_grating_v02.fsp (258.4 KB)

Please help!

As you can see, I’m using the structure of Pz to plot it as a heatmap as a function of angle and frequency. I want to do the same thing, but now for the far-field. Can you please tell me how to do this?

Then I suppose there is no solution to my question using Lumerical FDTD.

sorry for the slow reply. it should be relatively straightforward to get the grating orders in the far field. We have some analysis group that should do this for you, see screenshot. We also have some examples that show this capability

square_diffraction_grating_v02.fsp (258.4 KB)

Not sure how much the near field Pz data can tell you accurate information. It is typically recommended to analyse the grating order information in the far field.