Optical Harmonics Generation under the Interaction of Intense (up to 1014 W/cm2) Mid-Infrared Femtosecond Laser Radiation of a Fe:ZnSe Laser System with a Dense Laminar Gas Jet.

Low-order (fifth, seventh, and ninth) harmonics have been generated under the interaction of intense (I ~ 10¹⁴ W/cm²) femtosecond mid-infrared radiation of a laser system based on a Fe:ZnSe crystal (wavelength is 4.55 μm, pulse duration by the FWHM level of intensity is 160 fs, and the pulse energy is up to 3.5 mJ) with an argon jet (pressure is up to 10 bar) in the tunneling ionization regime (Keldysh parameter is ). The maximum energy efficiencies of the 5^th, 7^th, and 9^th harmonic generation are 2 × 10^–7, 6 × 10^‒9, and 3 × 10^–10, respectively. It has been established that nonlinear effects of propagation of generating radiation under an increase in the pressure of the gas jet begin to significantly affect the process of generation. [ABSTRACT FROM AUTHOR]