Propagation of a Short Subterahertz Pulse in a Plasma Channel in Air Created by Intense UV Femtosecond Laser Pulse

摘要

The evolution of the electron energy distribution function in the plasma channel created in air by the third harmonic of the Ti:Sa-laser pulse of femtosecond duration is studied. It is shown that strong nonequilibrium of such a plasma leads to the possibility to use the channel for guiding and amplification of few-cycle electromagnetic pulses in subterahertz frequency range at the time of relaxation of the energy spectrum in air determined by the vibrational excitation of the nitrogen molecules. The refractive index and the gain factor as a function of time, electron concentration and frequency of the amplifying radiation are obtained. The propagation of few-cycle radio-frequency pulses through the amplifying medium is analyzed.