Effects of refractive turbulence on coherent laser radar

The leading-order effects of refractive turbulence are calculated for a general coherent laser radar with beam-angle and beam-offset misalignment. The effects of refractive turbulence are important for 10-microm operation in the atmospheric surface layer for typical daytime conditions and paths longer than 3 km. The effects for near-infrared and visible wavelengths are more pronounced. The behavior of different parameter regimes are related to the scintillation scales of the transmitted beam. In certain cases, the small-scale scintillation structure produces a measure of beam misalignment that is more sensitive than the free-space case. The phase approximation of the extended Huygens-Fresnel principle is shown to be correct in the limit of large path-integrated refractive turbulence.