Multicharged optical vortices induced in a dissipative atomic vapor system
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We investigate numerically the dynamics of optical vortex beams carrying different topological charges, launched in a dissipative three-level ladder-type nonlinear atomic vapor. We impose the electromagnetically induced transparency (EIT) condition on the medium. Linear, cubic, and quintic susceptibilities, considered simultaneously with the dressing effect, are included in the analysis. Generally, the beams slowly expand during propagation and new vortices are induced, commonly appearing in oppositely charged pairs. We demonstrate that not only the form and the topological charge of the incident beam but also its growing size in the medium greatly affect the formation and evolution of vortices. We formulate common rules for finding the number of induced vortices and the corresponding rotation directions, stemming from the initial conditions of various incident beams, as well as from the dynamical aspects of their propagation. The net topological charge of the vortex is conserved during propagation, as it should be, but the total number of charges is not necessarily the same as the initial number, because of the complex nature of the system. When the EIT condition is lifted, an enhancement region of beam dynamics is reached, in which the dynamics and the expansion of the beam greatly accelerate. In the end, we discuss the liquid-like behavior of light evolution in this dissipative system and propose a potential experimental scheme for observing such a behavior. 2013 American Physical Society.