The Studies On Propagation Properties Of Laser Beams In Non-Kolmogorov Turbulence

The propagation properties of laser beams in turbulence have been extensivelyattracted many scholars’ interests due to their practical applications in free-spaceoptical communications and remote sensing and so on. For a long time, the studies onbeams propagation have been mainly based on Kolmogorov’s power spectrum ofrefractive index fluctuations, which has been widely accepted. However, many inlandand overseas experiments have pointed out recently that Kolmogorov’s theory issometimes imcomplete to describe atmospheric turbulence statistics correctly,especially in portions of troposphere and stratosphere, and experimental datas havebeen largerly deviated from the predictions of the Kolmogorov model. In order tofully understand the influences of atmospheric turbulence on spatial opticalcommunications, it is much necessary to study the effects of the non-Kolmogorovturbulence on beams propagation. In this thesis, based on the non-Kolmogorov’spower spectrum of refractive index fluctuations, we mainly study the propagationproperties of elegant Laguerre-Gaussian (ELG) beams and partially coherenthigher-order cosh-Gaussian (ChG) beams in non-Kolmogorov turbulence, and thecorresponding numerical calculation and analysis are carried out. The main content isas follows:(1) Based on the extended Huygens-Fresnel principle, the analytical formulas forthe average intensity and root-mean-square (rms) beam width of ELG beams innon-Kolmogorov turbulence are theoretically derived. The influences of beamparameters and turbulence parameters on the normalized average intensity and therms beam width of ELG beams are numerically calculated.(2) Based on the extended Huygens-Fresnel principle and the unified theory ofcoherence and polarization, the formulas for the cross-spectral density matrix, thedegree of polarization and the spectral degree of coherence of partially coherent ELG beams in non-Kolmogorov turbulence are theoretically derived. Some numericalresults have been discussed the influences of beam order, initial coherence length,inner and outer scale of the turbulence on the polarization and coherence of partiallycoherent ELG beams, and the corresponding analysis have been shown.(3) Based on the extended Huygens-Fresnel principle and the second-ordermoments of the Wigner distribution function, the formulas for the average intensity,the rms beam width and the propagation factor (M2factor) of partially coherenthigher-order ChG beams are derived. We have investigated the propagationproperties of partially coherent higher-order ChG beams in non-Kolmogorovturbulence, and we also have detailedly discussed the difference influence betweenthe Kolmogorov’s power spectrum and non-Kolmogorov’s power spectrum onbeam’s propagation properties.