AC streamer discharge propagation assisted by femtosecond laser filamentation in a long air gap

We study the development of laser-guided, meter-scale electric discharges produced in air by a Tesla AC voltage generator. Using ultrafast imaging, we observe the propagation of streamers produced in the presence of femtosecond laser filaments when a 100 μs oscillatory voltage of 300 kV is applied to a rod electrode. We found that the streamers propagate much faster in the low-density gas channel formed by the filament when the voltage polarity is negative. Their propagation is unaffected by a grounded second electrode at the filament's end. The filament extends the length of the discharge by at least one order of magnitude, enabling the rapid formation of a bright, conductive plasma channel, whose characteristics resemble a leader.