Gas-induced solitons.
The self-guiding of femtosecond laser pulses in air is investigated. For powers close to the threshold for self-focusing, we show that the balance between the nonlinear focusing of the beam and its defocusing by multiphoton sources produces a new kind of solitonlike structure. Over considerably long distances, the radial profile of the pulse relaxes to a steady-state shape, whereas its temporal profile shrinks along propagation. The influence of the normal group-velocity dispersion is finally discussed.
Bergé
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L
Commissariat à l'Energie Atomique, Département de Physique Théorique et Appliquée, B.P. 12, 91680 Bruyères-le-Châtel, France.
Couairon
A
A