Generation and amplification of sub-THz radiation in a rare gases plasma formed by a two-color femtosecond laser pulse

摘要

A new approach to constructing the source of radiation in the sub-THz frequency range is discussed. It is based on the strong-field ionization of heavy rare gases with Ramsauer minimum in the transport cross-section by a two-color (omega + 2 omega) femtosecond laser pulse. Then a four-photon nonlinear process Omega = omega ' + omega '' - 2 omega ''' (omega ', omega '' are the frequencies from the spectral width of the pulse with frequency omega, and omega ''' is the frequency from the spectral width of the second harmonic 2 omega) with a transition to the initial state results in a low-frequency spontaneous emission that can be amplified in the strongly nonequilibrium laser plasma if the position of the photoelectron peaks is located in the region of growing energy transport cross-section.