Femtosecond self-guided atmospheric light strings

The onset and recurrence of multiple filamentary structures in the long-dis tance propagation of high power femtosecond laser pulses in air displays fe atures analogous to strong turbulence events observed in many areas of phys ics. However, dissipation is not a key player in regularizing the underlyin g singular dynamical events. The collapse singularity of the two-dimensiona l (2D) nonlinear Schrodinger equation is identified as the robust nonlinear mode which both initiates and sustains the waveguide. Physical collapse re gularization mechanisms include normal group velocity dispersion and plasma generation in the high intensity nonlinear focal regions. Plasma absorptio n is weak and the dominant process is the transient generation of a highly localized strongly defocusing lens which evacuates the light behind the lea ding intense light filament. Consequently the nonlinear waveguide formed is highly dynamic. (C) 2000 American Institute of Physics. [S1054-1500(00)017 03-1].