Scintillation of a gaussian beam reflected by a point target.

Free space optical beam propagation is largely limited by the visibility of the channel at a particular location and at a particular time. In the absence of highly scattering particles, such as rain drops and snow flakes, the scintillation is the most severe limitation to system performance in an optical channel. An area of application mathematically similar to optical communications is laser radar. In a laser radar, a beam is transmitted through a channel, the atmosphere in our case, reflected by a target and received either at the same location it was transmitted from (monostatic channel) or another location (bistatic channel). Knowledge of the scintillation of the reflected beam could not only help design an appropriate receiving system, but could also give information about the reflecting object that could be utilized in forming its optical signature. Using our recently developed theory, we calculate the scintillation of a gaussian beam propagating through atmospheric turbulence and reflected by a point target. The double pass scintillation is investigated for monostatic and bistatic channels and results are compared with our experimental data collected by the an eight aperture heterodyne detection system.