Study Of The Influence Of Atmospheric Turbulence On The Beam Quality Of Vortex Beams

The transmission properties of laser beams through atmospheric turbulence play a very important role in optical communications, laser radar, satellite remote sensing, and aerial mapping etc, thus causing long-term concern to researchers. Through a large number of theoretical and experimental researches of vortex beams, researchers found that the influence of atmospheric turbulence on vortex beam is smaller than that on the non-vortex beam. This paper is to discuss the beam quality of Gaussian Schell-model(GSM) vortex beams and partially coherent flat-topped vortex beams propagating through atmospheric turbulence, specific contents are as follows:Based on the Von karman spectrum, using the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function(WDF), the analytical expressions for the beam propagation factor(namely 2M factor) and angular spread, the WDF and kurtosis parameter, and the Sterhl ratio(SR) of GSM beams propagating in atmospheric turbulence are derived and the numerical simulation were carried on. According to the analysis of the 2M factor and angular spread of GSM vortex beams, we can obtain that the larger the propagation distances z, the structure constant and the spatial correlation length s0 are, as well as the smaller the inner scale l0 and the wave length l are, the larger the 2nC2 M factor and the angular spread are. According to the analysis of the WDF and kurtosis parameter, we can obtain that the smaller the propagation distances z and the structure constant are, as well as the larger the inner scale l0 is, the larger the normalized WDF and the smaller the kurtosis parameter are; the smaller the wave length l and the larger the spatial correlation length s0 are, the smaller the normalized WDF and the kurtosis parameter are. According to the analysis of the SR, we can obtain that the smaller the structure constant, the inner scale l0 and the wave length l, as well as the larger the outer scale turbulence L0, the lager the SR, and as the spatial correlation length s0 increases, the SR first increase then decrease. In 2nC2nC addition, non-vortex beam is more easily affected by turbulence than vortex beams.The analytical expressions for the 2M factor of partially coherent vortex beams propagating through Von karman atmospheric turbulence are derived and the numerical simulation and analysis was carried on. It is shown that the larger the propagation distances z, the structure constant, the spatial correlation length ?0 and the beam order N, the smaller the inner scale l0 and the wave length ?, the smaller the 2nC2 M factors are, the less the propagation of partially coherent flat-topped vortex beams is affected by atmospheric turbulence, and the better the beam quality is. Compared with the partially coherent flat-topped non-vortex beam, the partially coherent flat-topped vortex beam is more beneficial to the beam propagation through atmospheric turbulence and is more conformable to be applied to the atmosphere laser communications. Through the selection of suitable beam parameters and turbulence parameters, the influence of atmospheric turbulence on beam quality can be effectively reduced.