| It is well known that optical communication exhibits significant advantages in terms of high speed,high bandwidth and anti-interference as compared with microwave communication.Unfortunately,the random fluctuations in the index of refraction of atmosphere cause spreading of a light beam beyond that due to pure diffraction,beam wander,loss of spatial coherence,and random fluctuations in the irradiance and phase.These effects can seriously degrade the signalto-noise ratio of an optical heterodyne receiver and limit the application and development of laser in the field of atmospheric optics.In recent years,numerous efforts have been paid to the propagation properties of partially coherent beams and it has been shown theoretically and experimentally that compared with completely coherent ones,partially coherent beams can effectively reduce the negative effects of atmospheric turbulence by adjusting their polarization,amplitude,coherence and phase.On the other hand,the twisted beams not only carry the orbital angular momentum,but also enhance the anti-turbulence self-repairing capability,which have important applications in optical tweezers and laser atmospheric transmission.In this paper,based on the theory of devising genuine spatial correlation functions of partially coherent beams and the combination of twist phase,we propose partially coherent Laguerre Gaussian pseudoSchell mode(LGPSM)beams and twisted rectangular Laguerre-Gaussian correlated Schell mode(TRLGCSM)beams,and study their propagation characteristics in atmospheric turbulence.Firstly,based on nonnegative definiteness of the corresponding cross-spectral density(CSD)function to devise genuine spatial correlation functions of partially coherent beams,we introduce LGPSM beams and study the statistical properties focused by a thin lens.Results show that in a certain range of propagation distances,their radiance profile becomes narrower and pret at the beam waist and presents a ring-shaped profile in the focal plane.Secondly,a new class of twisted sources named rectangular Laguerre–Gaussian Schell mode(TRLGCSM)fields is introduced based on a superposition of a mutually incoherent,tilted and displaced partially coherent beams,and then extended to the vector field.With the help of generalized Huygens-Fresnel integral formula,the analytical expressions for the CSD of a TRLGCSM beam in scalar and vector form propagating through anisotropic non-Kolmogorov turbulent atmosphere are derived.The evolution characteristics of the beam such as the spectral intensity,the spectral degree of coherence,and the degree of polarization are investigated in detail.These results show anisotropy of turbulence causes an anisotropic spreading of coherence,intensity and polarization of beams in the horizontal and vertical directions.Due to the existence of twist phase,the influence of atmospheric turbulence on the beam can be effectively suppressed.Finally,the analytical expressions for the second-order moments of scalar and vector TRLGCSM beams and LGPSM beams propagating in atmospheric turbulence are derived,and the statistical characteristics of M 2 factor of each beam are analyzed in detail.The results show that a scalar or vector TRLGCSM beam with lower coherence,larger twist factor and larger mode order m,n can effectively reduce the influence of atmospheric turbulence.In addition,compared with the LGSM beam,LGPSM beam has better beam quality propagating in atmospheric turbulence. |
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