Spectral changes in electromagnetic stochastic beams propagating through turbulent atmosphere

It is known that the spectrum of light can change on propagation, even in free space. Such changes are due to its coherence properties. We determine how the spectrum of a stochastic electromagnetic beam of any state of coherence changes on propagation in atmospheric turbulence. We illustrate the results by examining changes in the spectrum of an electromagnetic Gaussian Schell-model beam whose spectrum consists of a single spectral line with a Gaussian pro. le, which propagates through atmospheric turbulence, with Kolmogorov power spectrum. The results are of interest for optical communications through the atmosphere and for laser radar systems.