Wrong laser waist value when using LASY about fbpic HOT 3 OPEN

Thanks for raising this issue.

If I understand your question correctly, I think that you are saying that, in the above example, ts.get_laser_waist returned a different value than the one you expected (3 microns, i.e. the spot size that you used in Profile.txt file).

I think that the above observation is in fact expected, because of the line laser.propagate(150.e-6) in your Profile.txt. This line means that the laser is to be initialized 150 microns after its focal plane. Because the Rayleigh length here is shorter than 150 microns, the laser waist of the laser will be very different than 3 microns at initialization.

So, in short, I don't think that there is a bug here. If you remove laser.propagate(150.e-6), you should now see the expected waist.

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Thanks for your answer, I think laser. propagate should be fewer than Rayleigh's length, is it true?

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Hm, in principle, laser.propagate can be used for distances longer than the Rayleigh length ; it all depends on what you want to simulate...

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