Amplification and Guiding of Microwave Radiation in a Plasma Channel Created by an Ultrashort High-Intensity Laser Pulse in Noble Gases

We develop an analytical model of the evolution of a plasma channel produced in rare gases (argon and xenon) by a femtosecond KrF laser pulse. We show that the strong nonequilibrium of the photoelectron energy spectrum and the presence of the Ramsauer minimum in the transport scattering cross section makes the channel optically more dense as compared to the non-ionized gas in the microwave frequency band, and consequently such a channel appears to be a waveguide. In xenon, this nonequilibrium state of the plasma leads to the transportation and amplification of the microwave signal during the relaxation process of the photoelectron energy spectrum.