# Incoherent simulation

#1

Hi,

Is it impossible to get incoherent results of far field? I would like to reproduce sunlight in FDTD.

#2

Hi,

https://kb.lumerical.com/en/index.html?ref_sim_obj_fdtd_coherence_incoherent_dipole.html

In the example, it has 2 dipole for spatial incoherent. However if you want more than 2 dipole for “spatial incoherent” then you can use the sum operator in the sweep tab that will apply a simple sum over the farfield results (which is a matrix).

The intensity E2 of 2 dipole with spatially incoherence will calculate by simulating each dipole and measure intensity each dipole, then 2 intensity of 2 dipole will be sum. And we will have the intensity of 2 dipole with spatially incoherent E1^2+E2^2.

The reason is that you are simulating one dipole at a time (using sweep) and then adding the farfield results, you are incoherently summing the farfield intensity results. However, to calculate the coherent farfield results, you need to simulate all dipoles in one simulation.

https://kb.lumerical.com/en/index.html?ref_sim_obj_fdtd_coherence_temp.html

https://kb.lumerical.com/en/index.html?oleds_simulation_methodology.html

Hope this helps.

#3

So, to reproduce sunlight in FDTD, do I have to use multiple dipoles, right?

I’ll try it, thank you.

#4

Yes.