Four-wave mixing in molecular gases under filamentation of the collimated femtosecond beam

Abstract

The four-wave mixing process during a single-color femtosecond filamentation in the molecular gas is observed experimentally. The role of the seed is represented by the self-shifted to infrared region Raman bullet and the new blue-shifted component burns up as a result of the interaction between the Raman bullet and the reservoir radiation. The blue-shifted component propagates along the beam axis. The theoretical analysis of the four-wave mixing process synchronism shows that the on-axis forward propagation of the blue-shifted component occurs when the plasma concentration is higher than a certain threshold (3.3 × 1016 cm−3 at the fundamental wavelength of 800 nm).