Effects Of Turbulence Aberration On The Focal Beam And Photon's Orbital Angular Momentum In The Atmospheric Optical Communication

The theoretical research of laser beam propagating in the atmosphere is of great importance in the field of laser communication, radar, laser weapons, and so on. The effects of atmospheric turbulence on laser beam are in a prominent position. This thesis mainly focuses on the influence of slant and horizontal path turbulent atmosphere on the laser beams with different source properties.Based on the extended Huygens-Fresnel principle and the quadrature approximation of phase structure function, the intensity distribution properties on the focal plane of coherent and partially coherent vortex beams propagating through the turbulent atmosphere were investigated with the application of numerical simulation. The analytical expressions for intensity distribution of partially coherent hollow beam propagating through the turbulent atmosphere and for cross spectral density of partially coherent flat-topped beam propagating through the turbulent atmosphere were obtained by the use of tensor integral method. By expanding the circular aperture function into the superposition of complex Gaussian function, the expression of axial intensity distribution of truncated Bessel-Gauss beam propagating through the turbulent atmosphere was derived. The analytical formulas of cross-spectral density, intensity distribution and beam spreading for J 0-correlated partially beam propagating through the turbulent atmosphere were obtained. The effects of the atmospheric refraction index structure constant, zenith angle, focal distance, beam topological charge, turbulence outer scale, etc. on the intensity distribution and spatial coherence on the receiver were studied for above-mentioned different types of beams with detail. The stronger the turbulence, the faster the disappearance of fluctuating phenomenon for the spatial coherent degree of beams propagating in the atmosphere.By decomposing the turbulence total aberration into turbulence tilt aberration, turbulence defocus aberration, turbulence astigmatism aberration, turbulence coma aberration and so on, the effects of atmospheric turbulence low-order aberrations on the measurement probability of the orbital angular momentum (OAM) using OAM states of single photons in free-space optical communication were studied. The higher the turbulence aberration order, the weaker its effects on the measurement probability of the OAM. It should correct wavefront tilt aberration firstly in the aberration correction of adaptive optics.