Energy exchange process among multiple filamentary femtosecond laser beams in air

Abstract

Energy exchange between two filamentary pulses was demonstrated in several experiments [1-4], and the energytransfer direction depends on the time delay between filamentary pulses, the initial chirp, the laser intensities, the location, the crossing angle and the relative polarization. However, the understanding of the physical mechanisms of energy exchange in literatures are different and puzzling, including the impulsive Raman nonlinear response of themolecules [1], the plasma-mediated forward stimulated Raman scattering [2], the traveling plasma grating [3], and the classical two beam coupling model [4]. In this Letter, we study the energy exchange between a delay-tuned beam and two delay-fixed beams with a small angle (3.7o), keeping in mind underlying physical mechanisms of energy exchange. Unexpectedly, we find a previously undocumented energy exchange within approximate 60 ps with the presence of plasma grating.