Phase Synchronism in the Generation of Harmonics in Gas Taking into Account Changes in the Wave Vector Detuning during the Propagation of an Intense Femtosecond Laser Pulse

An alternative approach to determining the conditions of phase synchronism in the generation of harmonics in gases is proposed to take into account changes in the wave vector detuning during the propagation of an intense femtosecond laser pulse. Based on a numerical study of the third-harmonic generation by an argon medium, laws of scaling laser radiation absorption in the medium and of the phase modulation of spectral field components, which link macroparameters of interaction (pressure, intensity, and degree of medium ionization), have been identified. The possibility was investigated of increasing the third harmonic signal by increasing the gas jet pressure while keeping absorption at a low level.