Study On The Characteristic Of Laser Beam In The Slant Path Through The Atmospheric Turbulence

This thesis emphasizes on the research of the theory and experiments of the laser beam propagation in the atmosphere, which are of great importance in the areas of laser radar, laser missile-guidance and communication. Since the effects of turbulent atmosphere on the laser beam propagation in the atmosphere,this paper researches mostly the effect of the turbulent to the laser in the atmosphere. Firstly, the simplified index of refraction spectral density function including the effect of the inner and outer scale of the turbulent is given, secondly, the thesis puts much emphasis on three phenomenon of the laser under the effects of turbulence, i.e., intensity fluctuation (scintillation), beam spreading and wander, phase fluctuation. Based on strong fluctuation theory, the mutual coherence function of laser beam propagation in the atmospheric turbulence, according to Huygens-Fresnel and Mellin transform techniques, log-amplitude fluctuation variance,spreading radius and spreading angle are obtained, and applying the ITU-R turbulence structure constant model which is altitude dependent to calculate the spreading radius and spreading angle with different height of drone in the slant path. The Mellin transform techniques is applied to the wander effects of the collimating laser beam propagation in atmospheric turbulence in the slant path with different height of drone and different outer-scale of turbulence. Finally, this paper analyes the experiment dates of two wavelengths that are 1.315μm and 3.8μm laser collimated beam.