Coherence of a Bessel beam in a turbulent atmosphere

Features of the formation of an optical Bessel beam in a turbulent atmosphere are studied on the basis of a solution of an equation for the second-order mutual coherence function of the field of a Bessel optical beam. A condition has been derived for the mean intensity of a Bessel beam, which is a quantitative criterion for the formation of a beam along a long path in a turbulent atmosphere. The behavior of the degree of coherence of an optical Bessel beam versus beam and turbulent atmosphere parameters has been studied. It was found that the degree of coherence of a Bessel beam typically oscillates at low levels of fluctuations in a turbulent atmosphere, and the number of maxima and minima unambiguously depends on the Bessel beam parameter (the wave vector component normal to the radiation propagation direction) at the same level of atmospheric turbulence. At high levels of fluctuations in a turbulent atmosphere, the degree of coherence of a Bessel beam is described by a single-scale dropping curve that approaches the similar characteristic curve of a spherical wave, with an increase in the level of fluctuations along the path of laser beam formation.