The effects of polarization changes of stochastic electromagnetic beams on heterodyne detection in turbulence

Abstract

The performance of heterodyne systems is discussed for stochastic electromagnetic beams in turbulent atmospheres by introducing a turbulence spectrum of refractive-index fluctuations. Several analytic formulae for the heterodyne detection system are presented by employing the beam coherence polarization matrix of an electromagnetic Gaussian Schell-model beam. Based on the Tatarskii spectrum model, some numerical results are given for the variation of heterodyne efficiency with the misalignment angle, detector diameter, turbulence conditions and parameters of the overlapping beams. According to the numerical results, we find that the change in heterodyne efficiency is dependent on the initial polarization of the beams, and that a turbulent atmosphere degrades the heterodyne efficiency significantly for a lager detector diameter. The change in heterodyne efficiency in a turbulent atmosphere is basically the same as that in free space for a relatively short distance zs. However, the change in heterodyne efficiency is different for a sufficiently long distance. For the deterministic received signal and the detector, the performance of the heterodyne detection can be adjusted by controlling the local oscillator signal parameters.