Post-filamentation multiple light channel formation in air

Abstract

Multiple light channels without ionization have been observed over a long distance at the post-filamentation stage during the propagation of an intense femtosecond laser pulse in air. It was found that after the filamentation ended, the laser beam was divided into multiple distinguished millimeter-scale spots surrounded by a larger low energy background. These spots propagated with low divergence, significantly lower than that given by the nonlinear propagation of a laser beam with similar diameter (FWHM) and power. The corresponding numerical simulation reveals that the low intensity energy background plays a dominant role in inducing these multiple light channels at the post-filamentation stage.