Learning Forum

[Another]

For example.

If I set the laser source at position (0, 0, 0) ==> x = 0 um, y = 0 um, z = 0 um

and I want to shot the laser beam pass Air medium to another metal sheet like Au or Cu being far away 500 um or 1000 um.

Besides, I want to collect a transsmision value both before and after laser beam pass the metal sheet.

How can I do this in the FDTD simulation?

[Taylor Robertson]

Hello If it is a simple Gaussian, the you can probably just calculate the spot after propagating this distance if you know the beam waist and focal length. Look at the beam options tab in the following article.
https://support.lumerical.com/hc/en-us/articles/360034382854-Plane-wave-and-beam-source-Simulation-object
To propagate more complicated fields through free space it is best to use Lumericals far field projection methods. If you want to look at the result of passing through a lens system the I would use a ray tracer like Zemax. FDTD is very expensive, and without anything to interact with the fields will behave predictably, so FDTD would be overkill.
To do this please refer to the farfield documentation. You can specify the plane of interest, then call farfieldexact on the Gaussian beam profile, then import this a a source for second FDTD simulation.
Best