Abstract

A study of the possibility of triggering lightning with optical pulses has been investigated. A theoretical analysis shows that a continuous ionized path of several tens of meters should be created. In recent experiments, long focal length lens were used to confine a low energy (≈ 200 μJ) femtosecond ultra-violet laser pulse, resulting in a weak ionization (< 10⁻⁶ of the air molecules) in a column between two electrodes spaced by 25 cm. A discharge was induced with this technique at half the self breakdown field of air [1]. The mechanism of laser induced guided discharge is a local field enhancement resulting from the migration of charges in the applied electric field. This mechanism is different from the standard laser induced spark gap, where the laser energy is sufficient to induce a plasma between the electrodes. Self-trapped filaments can create a continuously ionized path over very long distances, which is the main requirement for “seeding” and guiding a discharge over long distances with minimal laser energy.

© 1994 Optical Society of America