Nonlinear self-focusing of incoherent array beams in the turbulent atmosphere

The nonlinear self-focusing effect on the beam quality of powerful incoherent array beams propagating upwards in the turbulent atmosphere is investigated. A quadratic approximation of the nonlinear phase is proposed, and the analytical propagation formulae of incoherent array beams in the turbulent atmosphere are derived and confirmed. It is shown that the beam quality at the target degrades as the fill factor fc increases due to an increase of self-focusing, but it becomes better as the number N of sub-beams increases because of a decrease of self-focusing. Furthermore, the detrimental self-focusing may be even eliminated when fc is small enough or N is large enough. On the other hand, it is found that in the turbulent atmosphere, an incoherent array beam can achieve a higher threshold critical power, a higher intensity and a higher energy focusability at the target than a single laser beam. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.