Wave Structure Function and Mutual Coherence Function of an Optical Wave in a Turbulent Atmosphere

The most commonly used expression for the wave structure and mutual coherence function for an optical wave propagating in a turbulent atmosphere, which is based on an unphysical extrapolation of the Kolmogorov spectrum, is shown in general to be incorrect. For a modified spectrum, we show that the correction to the wave structure and mutual coherence functions, the implied resolution, and the resulting signal-to-noise (S/N) ratio using heterodyne detection, are considerable. Approximate expressions for the coherence function, valid over three distinct propagation distance regions, are derived, and experimental evidence in support of our results is cited.