Wake dynamics of air filaments generated by high energy picosecond laser pulses at 1 kHz repetition rate *

An investigation outlining filamentation in air of 7 picosecond lasers pulses up to 200 mJ energy from a λ = 1.03 μm Yb:YAG laser at repetition rates up to f = 1 kHz is presented.  Interferograms of the wake generated show that while pulses in a train of repetition rate f = 0.1 kHz encounter a nearly unperturbed environment, at f = 1 kHz a channel with an axial air density depression of ~ 20% is generated and maintained at all times by the cumulate effect of adjacent pulses. Measurements at f = 1 kHz show that the energy deposited decreases proportional to the molecular channel density depletion, which becomes more pronounced as the repetition rate and pulse energy increase.  Numerical simulations provide insight into the dominant energy loss mechanisms. The results are of interest for the atmospheric propagation of joule-level picosecond pulses from Yb:YAG lasers, of which average powers now surpass 1 kW, and for channeling other directed energy beams.