The effect of atmospheric turbulence on the propagation properties of optical vortices formed by using coherent laser beam arrays

Abstract

In this paper, we consider the effect of atmospheric turbulence on the propagation of an optical vortex, which may be formed from a radial coherent laser beam array with an initially well-defined phase distribution. The propagation formula of the radial coherent laser array passing through a turbulent atmosphere is analytically derived by using the extended Huygens–Fresnel diffraction integral. Based on the derived formula, the effect of the atmospheric turbulence on the propagation properties has been studied in great detail. Our main results show that atmospheric turbulence may result in the prohibition of the formation of the optical vortex or the disappearance of the formed optical vortex, which are very different from the behaviour in free space. An optical vortex formed with higher topological charge may propagate over a much longer distance in a moderately or weakly turbulent atmosphere. After sufficient long-distance atmospheric propagation, the output beam (initially with different phase distributions) finally loses the vortex property and gradually becomes a Gaussian-shaped beam, and in this case the output beam actually becomes incoherent light fields due to the decoherence effect of the turbulent atmosphere.