The most recent developments on the propagation of optical beams in a turbulent medium, such as the clear atmosphere, are reviewed. Among the phenomena considered are beam spreading, beam wander, loss of coherence, scintillations, angle-of-arrival variations, and short-pulse effects.

Electromagnetic beam propagation in turbulent media

Reviews the major advances achieved in the studies of EM wave propagation in turbulent media. The greatest attention has been directly to the problem of strong fluctuations of intensity. The theoretical results of this treatise include: the path integration technique, the predominant correlation method, the two-scale method, the hybrid approach to scattering from small inhomogeneities in the presence of large ones, the theory of coherent channels in backscattering, and the concept of partially determinate processes and fields. New physical effects described in the review include the rise of the coherence radius in intermittent turbulence, backscatter enhancement, doubling the variance of phase, incidence angles, group delay, and frequency shifts in the double passage of waves through turbulent media, the residual scintillation effect, the long correlation effect in backscattering, the partial reversal of wavefronts in turbulent media, the magic cap effect in reflection from phase conjugated mirrors, the strong localization of UHF radio waves in stochastic tropospheric waveguides, the effect of penetration in caustic shadows, and enhanced translucence. New fields of experimental research have been outlined, such as scattering from vegetation and snow covers, and coherent structures in turbulence, and new objects of theoretical analysis have been elicited: random dislocations of wavefronts, fractal and critical wave phenomena, and the predictability of random fields.

https://iopscience.iop.org/article/10.1088/0034-4885/55/1/002/pdf

Propagation of electromagnetic waves through a turbulent atmosphere

A series expression is developed for the fourth moment of a beamed field incident on a random phase screen or an extended medium. The series has a symmetry that allows its first few terms to generate useful approximations at both low and high spatial frequency. The parabolic wave equation, the Markov approximation, and Gaussian refractive index fluctuations are assumed. The result for the phase screen is obtained by Green's function techniques. The extended-medium result is derived in an analogous manner by using path integral methods. The same results are also derived by moment-equation methods. The behavior of the leading terms is compared to previous results for plane-wave and point-source geometries.

Solution for the fourth moment of waves propagating in random media

A number of atmospheric phenomena affect the propagation of light. This article reviews the effects of clear-air turbulence as well as atmospheric turbidity on optical communications. Among the phenomena considered are astronomical and random refraction, scintillation, beam broadening, spatial coherence, angle of arrival, aperture averaging, absorption and scattering, and the effect of opaque clouds. An extensive reference list is also provided for further study, Useful information on the atmospheric propagation of light in resolution to optical deep-space communications to an earth-based receiving station is available, however, further data must be generated before such a link can be designed with committed performance.

/pdf/atmospheric-propagation-effects-relevant-to-optical-4j4l14lngy.pdf

Atmospheric propagation effects relevant to optical communications

The asymptotic theory has been used to calculate the effect of the inner-scale size of the eddies on the properties of the irradiance variance and covariance of a plane wave propagating in a turbulent medium. It is found that the inclusion of a finite inner scale leads to an increase in the irradiance variance over what is predicted in the limit when the inner scale is zero. In addition, the inclusion of a finite inner scale alters the results for the spatial scales over which the irradiance scintillations are correlated. Finally, the results obtained are compared with recent predictions obtained by using the heuristic theory.

Inner-scale size effect on the scintillations of light in the turbulent atmosphere

The spectral and correlation properties of intensity fluctuations of irradiance of a focused transmitter, beyond a layer of rubulent atmosphere, are studied. Of particular concern is the range of large values of the phase structure function, computed on the transmitter aperture size, where saturation of fluctuations is predicted. The analysis is based on the phase-screen approximation.

K.S. Gochelashvily

Papers

Focused Irradiance Fluctuations Beyond a Layer of Turbulent Atmosphere