Initiation of high-voltage discharge in air by a plasma filament produced by an intense femtosecond laser pulse

High-voltage discharge initiated in air by a plasma filament produced by an intense femtosecond laser pulse was studied experimentally. It is found that the threshold of a laser-induced discharge decrease three-fold as compared to that of a discharge in undisturbed air. It is shown that the formation time of a laser-induced discharge decreases by almost three orders of magnitude as the applied voltage increases by a factor of 2. A numerical model of the discharge process is developed that adequately describes the experimental results. In particular, simulations reproduce the experimentally observed steep dependence of the formation time of a laser-induced discharge on the applied voltage, as well as typical values of the electric field required for such a breakdown.