Incoherent beam propagation with POP

Question

HiI am trying to propagate a matrix of independent Gaussian beams incoherently, but for some reason it seems that the beams are still interfering with each other (i.e. it seems that the POP is propagating the beams coherently).I have defined the beams as incoherent in a Multimode file:  Which looks like this: In the far field the intensity looks like this: It looks like there is interference (side lobes). Its possible to see it more clearly with a cross-section:If the propagation was incoherent, then the intensity should not dip where I have indicated with the red arrows, right? In addition, I am getting a nonsensical beam parameter product which is too low and implies coherent propagation. Maybe this is a problem with sampling or window size? Or syntax in the Multimode file?Can anyone help? :)

Kevin Scales · Accepted Answer

The issue here is that while you can define the multimode beam using the INCOHERENT or COHERENT commands to control the initial phase, the subsequent propagation is always coherent. POP does not perform incoherent propagation.

A better approach in this case might be to perform four separate propagations and then use ZPL to write a macro that can perform an incoherent sum using ZBFSUM and the value of zero for the first parameter.

Dror Shayovitz · Answer

Thanks for the explanation Kevin!

Incoherent beam propagation with POP

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