## Photonics

#### 3d far field

• quantumoptics
Subscriber
• Greg Baethge
Ansys Employee

Thanks for posting your question on the forum. Ansys employees are not allowed to download any file posted here (see this post), so to be able to help you, could you provide further details on how the simulation is set and the script you are using as well as the error you get. You can post screen copies of the simulation settings, for example.
• quantumoptics
Subscriber
Thanks for your reply . I try to simulate the 3d model of a 2 slit . and get the far field from that. I want to plot the far. field distribution and my plot axis be wavelength vs angle. I did it in 2d FDTD and could get the result but for 3d I couldnt have it. here is how I simulate the structure and the script would be as follow like the picture. in my script the only change I made is the , I change the farfieldexact2d to 3d. my monitor is 2D monitor z normal .

• Greg Baethge
Ansys Employee
Thanks for the additional information,. I think there's a problem in how you define the projection location. The monitor is z normal, and the projection is done at z=112nm, unless the monitor is far from this position (at least 1 wavelength away). the far field calculation might not have much sense. Additionally, you calculate theta from x and y, it should be from x and z.
In any case, it might be simpler to start from theta, we can calculate the field at a distance of 1m, x,y and z are obtained from theta and we use farfieldexact to get the far field vs x(theta), 0, z(theta). It could be something like:
theta = linspace(-90, 90, 181);
y =0;
E = farfieldexact(m, x, y, z, 1:nf, 1.5);
E2 = sum(abs(E)^2, 2);
image(theta, lambda*1e6, E2/max(E2), "angle", "lambda (um)");
I hope this will help!