Laser multiple filamentation control in air using a smooth phase mask

We report on experimental results revealing the important role of linear diffraction in multiple filamentation of intense laser pulses propagating in air. We show that during the early stages of propagation the transverse energy redistribution is governed by the laws of classical optics, defining the initial conditions for subsequent filamentary breakup of the beam. This is done by introducing a smoothly varying transverse phase, resulting in deterministic multiple filamentation. The observations presented here indicate precise wave-front shaping as a way to control the highly nonlinear and otherwise turbulent aforesaid process, which is a prerequisite for a number of applications.