While propagating through the atmosphere ultrashort highly intense laser beams break up into spatially trapped “light bullets”
(filaments) that can propagate many diffraction lengths without diverging. These self-guided beams have many potential
applications such as remote-sensing of the atmosphere and lightning control.
The figures in the right show the white light that is emmited from a filament (left), and connical emmision in the forward
direction (right).
The standard explanation for filamentation of intense laser beams relies on dynamic balance between the focusing Kerr
nonlinearity, diffraction and the defocusing effect of plasma formation due to multiphoton ionization.
n=n0+n2-w2p/2w2
This description is a bit naive and does not reveal the full complexity of the problem, but it gives good intuition to the key
physical mechanisms.
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