Formation and evolution of intense, post-filamentation, ionization-free low divergence beams

The mechanisms related to the formation and propagation of post-filamentation intense light channels were rigorously investigated experimentally and numerically. It was found that they originate from a hot spot formed by diffraction of the pulse energy reservoir onto the plasma. Once the hot spot was formed, a channel with intensity estimated at 0.5 TW/cm2 could maintain its diameter over several tens of meters such that air was not ionized, but the self-focusing produced was sufficiently high to balance linear diffraction. This propagation regime is of high interest to propagate high intensity laser pulses with limited losses.

Research Highlights
► The propagation of femtosecond pulses after filamentation in air was investigated experimentally and numerically over 50 m.
► A low divergence intense light channel, without ionization, was observed over the entire propagation path.
► This propagation regime is of high interest to propagate high intensity pulses with limited losses.