Atmospheric Turbulence Parameters Retrieved From Optical Beam Wander And Quality Factor And Related Research

As is known to all,the clear-air turbulence(CAT),and low-level wind shear closely related to low-altitude turbulence are recognized as important factors endangering aviation safety.Therefore,detecting atmospheric turbulence and wind shear is very important for aviation safety.For turbulence and wind shear in clear skies and dry weather conditions,lidar is the best detection technology because of its high accuracy,high resolution and long detection range.However,at present,such detection technology system is complex,expensive and there are still deficiencies in detection methods.In order to improve the existing lidar and put forward new detection techniques,it is necessary to carry out in-depth research on laser propagation in atmospheric turbulence.Therefore,on the basis of studying the propagation characteristics of two kinds of typical light beams in turbulent atmosphere,this thesis focuses on the joint inversion method of atmospheric turbulence parameters based on beam wander,M~2 factor and K parameter.1.Analytical expressions of M~2 factor,turbulent distance and Rayleigh distance of truncated Airy beam are derived,and the changes of M~2 factor,relative M~2 factor,turbulent distance and turbulent Rayleigh range with beam parameters are analyzed in detail by numerical analysis method.The results show that the beam quality is better when the turbulent structure constant is small,the inner scale and the truncation factor are large;the beam is less affected by the turbulence when the truncation parameter is small,and there is an optimal initial width,which makes the beam quality the best.The turbulent distance decreases with increasing structural constant,truncation factor,initial width of the first lobe,and decreasing inner scale.The turbulent Rayleigh range decreases with increasing structure constant,truncation factor,inner scale and initial width of the first lobe.2.The simplified integral expressions of M~2 factor and beam wander of partially coherent radially polarized circular Airy beams are derived.The influence of attenuation factor,scale parameter and coherence width on M~2 factor and beam wander is obtained by numerical simulation.The results show that the beam quality is poor when the propagation distance,turbulence intensity and outer scale are large.The root mean square beam drift and relative beam drift increase with the increase of coherence width,inner scale and turbulence intensity.The relative beam drift and root mean square beam drift decrease with the increase of transmission distance.Along with the increase of the initial radius of the scale parameter,and the relative increase with the decrease of the first beam drift,there is a low,this means that within the coherent width and smaller scales,turbulence intensity and larger transmission distance,the smaller the beam wander ups and downs,when the other parameters must exist a minimum scale parameters respectively,the initial radius and minimum beam drift.3.According to the M~2 factor and K parameters of truncated Airy beam,the structure constants and internal scales of turbulence refractive index in atmospheric turbulence are inverted,and the effects of each parameter on the inversion results are analyzed.Based on the power spectrum inversion method,a multilayer phase screen simulation program for truncated Airy beam propagation in turbulent atmosphere is completed.The spot intensity of truncated Airy beam with different truncated parameters and different initial beam width is simulated and the results are analyzed.The simulated beam wander is compared with the theoretical value under certain turbulence intensity,internal scale,beam width and truncation parameters,and the effectiveness of the inversion formula is verified.