title: Two-frequency mutual coherence function of electromagnetic waves in random media: a path-integral variational solution.
abstract: By use of path-integral methods, a general expression is obtained for the two-frequency, two-position mutual coherence function of an electromagnetic pulse propagating through turbulent atmosphere. This expression is valid for arbitrary models of refractive-index fluctuations, wide band pulses, and turbulence of arbitrary strength. The approach presented in this paper was examined in the cases of plane-wave, spherical wave, and Gaussian beam propagation in power-law turbulence and compared with existing numerical and exact results. A number of new results were obtained for the Gaussian beam pulse. Expressions derived here should be applicable to a wide range of practical pulse propagation problems.