Fast pulsed electric field created from the self-generated filament of a femtosecond Ti:Sapphire laser pulse in air

We present an experiment demonstrating the generation of fast pulsed electric field from a plasma column created in air as a result of the interaction of N-2 and O-2 molecules with a 220 fs laser pulse. By first measuring the distribution of N-2(+) and then by measuring the net charge present at different positions in the-focal region, we determined that this plasma column has an intrinsic dipole moment, which generates these pulses. The origin of this dipole moment was attributed to longitudinal separation of electrons due to ponderomotive acceleration of electrons created through multiphoton ionization of N-2 and O-2 molecules: (C) 2000 Elsevier Science B.V. All rights reserved.