Research On Spreading And Wander Of Laser Beam In Troposphere Atmosphere Turbulence

The research of the theory and experiments of the laser beam propagation in the atmosphere is of great importance in the area of laser communication, laser survey, aviation mapping, satellite remote and laser weapons. In this paper, main content focus on the spreading and wander effects of the turbulence on the laser propagation in the atmosphere. Firstly, the power spectral density function of refractive index is given including the effects of inner and outer scale of the turbulence. Secondly, the physical mechanism of optical-beam spreading, wander and Angle-Of-Arrival fluctuations are introduced for the laser Line-Of-Sight path propagation under the effects of atmospheric turbulence. The mutual coherence functions of laser beam propagation in the atmospheric turbulence are discussed by the Rytov Approximation and Markov Approximation (MA), respectively. The expression of the long-term optical-beam spreading radius is obtained by a quadratic approximation. The expression of optical-beam wander is obtained from above long-term optical-beam spreading formula and the MA. A new model of short-term optical-beam spreading in a turbulent medium is established by Rytov Approximation, Geometrical-Optics Approximation (GOA) and the Gaussian large-scale filter function. Thirdly, the laws of Angle-Of-Arrival fluctuations are discussed by GOA and Structure Function, respectively. Lastly, the horizontal paths atmospheric propagation model is extended to the ground-to-space path. Under taking into account outer scale of atmospheric turbulence, the characteristic of beam wander for the uplink path is calculated by applying the ITU-R turbulence structure constant model.