Multifilamentation of femtosecond laser pulses propagating in turbulent air near the ground

Kurzfassung

The propagation of femtosecond laser pulses in turbulent air near the ground is analyzed. Confining to a power regime distinctly above the critical power for self-focusing, i.e. , and concentrating on initial peak intensities around 2.5 x 10^11W/cm^2 , the onset and early evolution of multiple filaments are addressed. Making use of the turbulence phase-screen method, numerical simulations of the pulse propagation indicate that turbulence fields with spatial scales below 6 mm are able to induce the onset of multifilamentation. An analytical linear plane wave perturbation model of the underlying modulation instability of the pulse front is introduced in support of the computational results. By this means, insight into the amplification of an initial perturbation of the pulse front from the point of view of the spatial frequency domain is given.