Laser Beam Broadening in Atmospheric Propagation

By using the Born approximation and the Gaussian model for the correlation of refractive index fluctuations in the atmosphere, an expression for the power in the first-scattered field of the TEM∞ mode is obtained. It is demonstrated that the second-scattered field does not contribute to beam broadening in the lowest-order approximation. The total power in the first-scattered field is found. The transverse profile of the scattered power is shown to be a function of a single parameter ΘL, which depends strongly on the ratio of the beam radius to the scale of turbulence a/lo. Values of lo and the mean square fluctuation of the refractive index (n12) are determined in an illustrative comparison with experimental data of the theoretical profile of a broadened beam.