RESUMO
Three-dimensional numerical simulations and direct experimental measurements of the multifilamentation of femtosecond laser pulses propagating in air are quantitatively compared. Agreement is obtained in terms of the evolution of the filamentation pattern and in terms of the size and energy of the individual filaments through 12 m of propagation. These results are made possible by the combination of a massively parallel propagation code along with a nondestructive experimental diagnostic technique. Influence of the pulse duration is moreover addressed. The numerical calculations also show that single and multiple filaments exhibit almost identical spectral signature.
RESUMO
The influence of atmospheric aerosols on the filamentation patterns created by TW laser beams over 10 m propagation scales is investigated, both experimentally and numerically. From the experimental point of view, it is shown that dense fogs dissipate quasi-linearly the energy in the beam envelope and diminish the number of filaments in proportion. This number is strongly dependent on the power content of the beam. The power per filament is evaluated to about 5 critical powers for self-focusing in air. From the theoretical point of view, numerical computations confirm that a dense fog composed of micrometric droplets acts like a linear dissipator of the wave envelope. Beams subject to linear damping or to collisions with randomly-distributed opaque droplets are compared.