Postionization regimes of femtosecond laser pulses self-channeling in air

An optical self-guiding of femtosecond filaments in air is identified in a regime where plasma generation ceases to support the self-channeling process. Group-velocity dispersion is shown to keep the beam temporally and spatially localized upon a few meters by taking over the ionization of air molecules, once the pulse peak power becomes close to the self-focusing threshold. In this regime, the pulse undergoes slow splitting events that maintain a residual self-guiding with light intensities as high as 10 TW/cm2, as soon as the electron plasma density has fallen down below 10(15) cm(-3).

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