Plasma channel produced by femtosecond laser pulses as a medium for amplifying electromagnetic radiation of the subterahertz frequency range

The electron energy distribution function in the plasma channel produced by a femtosecond laser pulse with a wavelength of 248 nm in atmospheric-pressure gases was considered. Conditions were determined whereby this channel may be employed for amplifying electromagnetic waves up to the terahertz frequency range over the energy spectrum relaxation time ~10^-7 s. Gains were calculated as functions of time and radiation frequency. The effect of electron – electron collisions on the rate of relaxation processes in the plasma and on its ability to amplify the electromagnetic radiation was investigated.