QW1E.7.pdf CLEO:2013 Technical Digest © OSA 2013 Guiding of meter scale AC discharges by laser filamentation in air A. Houard 1 , G. Point 1 , Y. Brelet 1 , J. Carbonnel 1 , Y.-B. André 1 , B. Prade 1 , L. Arantchouk 2 and A. Mysyrowicz 1 1 Laboratoire d’Optique Appliquée, ENSTA ParisTech, Ecole Polytechnique, CNRS, 91761, Palaiseau, France 2 Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, Palaiseau, France Author e-mail address: aurelien.houard@ensta-paristech.fr Abstract: We study the guiding effect of femtosecond laser filaments on high-voltage electric discharges generated by a compact Tesla coil. Meter scale repetitive discharges are demonstrated. OCIS codes: (190.5530) Pulse propagation and temporal solitons; (350.5400) Plasmas During propagation of intense laser pulses through atmosphere, owing to a dynamic competition between Kerr self-focusing, diffraction and ionization induced defocusing, a contracted beam of high peak intensity can be formed over long distances, provided the pulse input power exceeds a critical value (Pc ~ 5 GW at 800 nm). During this process called filamentation [1], the pulse leaves in its wake a thin column of weakly ionized plasma (electron density ~ 10 16 cm -3 ). Plasma filaments proved to be particularly useful for remote manipulation of high voltage discharges [2-5] and are of great interest for applications such as the laser lightning rod, virtual plasma antennas for radiofrequency transmission, plasma aerodynamic control or high voltage switch. In this paper, we report experiments of laser-guided discharges obtained in air with high voltage bursts delivered by a compact Tesla coil (as seen on figure 1). Characteristics of the guided discharges are studied for electrode gaps ranging from 30 cm to 180 cm, allowing extraction of the average resistance of the plasma column. Reproducible guided discharges of 1 meter at a repetition rate of 10 Hz are demonstrated. Fig. 1 Integrated image of an unguided (top) and a laser guided Tesla discharge (bottom) between two electrodes separated by 30 cm. The laser beam is focused in air producing a continuous plasma column about 2 m long, touching tangentially the two spherical electrodes connected to the Tesla output. The Tesla generator provides bursts of voltage oscillations at 100 kHz with peak amplitude of about 350 kV. No electric discharge is produced by the Tesla generator in the absence of laser when the interelectrode distance is larger than 32 cm. Guided discharges activated by the filament are obtained up to an interelectrode distance of 180 cm corresponding to a decrease of 80 % of the breakdown voltage. This decrease is much higher than the one observed with DC or Marx generator which was limited to 30% or 50 % [2-3]. The triggering effect appears to be very sensitive to the laser arrival time with respect to the phase and amplitude of the Tesla voltage cycles. Indeed, we observe a high discharge probability when the laser shot occurs when the Tesla voltage is at its maximum (in both polarities), and a very low probability when the voltage is about null (figure 2).