Energy, spectral, and angular properties of post-filamentation channels during propagation in air and condensed media

High-power femtosecond laser pulses undergo large-scale transformations during filamentation in a nonlinear medium. Spatial transformations result in the formation of the post-filamentation channels—intense spatially localized light structures observed in the laser beam at the plasma-free stage of pulse propagation. We present the experimental results on the main characteristics of post-filamentation channels formed by the filamentation of Ti:sapphire laser pulses (744 nm, 90 fs) in air. Angular divergence, spectral composition, power, and temporal parameters of post-filamentation channels at different initial pulse energy are investigated. We study a specific cascade pulse filamentation regime when the post-filamentation channel is initially formed in air and then experiences recurrent filamentation in a condensed medium (fused silica).