Transmission Beam In The Turbulent Atmosphere

The propagation of laser beams in a turbulent atmosphere has attracted much attention due to its widely important practical applications, such as in connection with remote sensing, monitoring and optical communication. The refractive index fluctuation causes a variety of effects on an optical wave while propagating in turbulence. Therefore, there has been much research on the ways of reducing the turbulent effects on the propagating optical beam.In this thesis, the basic theory and some parameter of atmosphere turbulence, scintillation index and some important power models for refractive-index is introduced, which give a basis theory for the work of wave propagation in the turbulent media.According to the applied environment of ghost image, ghost imaging with partially coherent light radiation through turbulent atmosphere has been studied. The analytical ghost imaging formulas have been derived based on the classical optical coherent theory and the extended Huygens-Fresnel integral. The influence of the turbulence strength, propagation length, the source's transverse size and coherent width on the quality of the ghost imaging has been discussed. It is found that the larger the source's transverse size is, the better the quality of the ghost imaging. When the turbulence strength, propagation length and the source's coherent width increase, the quality of the ghost imaging decrease.Beams with spiral phase are regarded as vortex beams. Each photon of vortex carries orbital angular momentum (OAM), which can be used in information encoding. The study on the propagation property of vortex beams in turbulence is very important. The scintillation index of vortex beams in turbulence has been measured with a scintillation detector. Corresponding properties of a Gaussian beam and vortex beams with diffirent topological charge propagating through the same atmospheric turbulence conditions are detected for comparison. The experimental data shows that vortex beams have inferior scintillation properties when compared with a comparable Gaussian beam and the scintillation index decreases with the increasing of the topological charge.Due to the the beam carries a vortex phase factor and nondiffracting, the generation and the propagation of Bessel beams is another subject that attracts much attention. The spatial light modulator(SLM) and axcion was used to generate high-order Bessel beams with desired topological charge. The propagation properties of high-order Bessel beams in a turbulent atmosphere has been studied experimentally with the effects of turbulence simulated by a rotated random phase plate. It is found that the high-order Bessel beams spreads due to the turbulence even in the non-diffracting distance. The effects of the turbulence can be reduced with increasing of the the topological charge which is the measure of the orbit angular momentum.