  High-power femtosecond laser radiation propagates nonlinearly in air
exhibiting pulse self-focusing and strong multiphoton medium ionization, which
leads to the spatial fragmentation of laser pulse into highly-localized light
channels usually called the filaments. The filaments are characterized by high
optical intensity, reduced (even zero) angular spreading and can contain laser
plasma or be plasmaless (postfilaments). The presence of optical turbulence on
the propagation path dramatically changes pulse filamentation dynamics and in
some cases causes pulse fragmentation enhancement and collapse arrest. For the
first time to our knowledge, we experimentally and theoretically investigate
the transverse profile of Ti:sapphire femtosecond laser radiation nonlinearly
propagating a 65 m air path to the region of postfilament evolution after
passing through an artificial localized air turbulence. We show that when a
turbulent layer is placed before the filamentation region, the average number
of high-intensive local fluence maxima ("hot points") in pulse profile as well
as their sizes grow as the turbulence strength increases, and then saturates at
some levels. On the contrary, the deposition of a turbulent screen within the
filamentation region has almost no effect on both the number and the average
diameter of the postfilaments.
