Depolarization Properties Of Polarized Laser Beams Propagating Through Turbulent Atmosphere

The laser technology has been applied widely and developed rapidly. It has sparked that the problems of laser beams propagating are paid attention and further researched. Polarization properties is one of important laser beams characteristics.The study of depolarization properties in laser beams propagation and the related issues also becomes a popular subject to many researchers at home and abroad. As yet,the partially polarized laser beams are mostly researched when they propagate through turbulent atmosphere. But the completely polarized laser beams are brought less attentions. The depolarization properties of the completely polarized laser beams are investigated in the paper in order to find out whether they propagating through atmospheric turbulence hold any advantages.In the paper, the expression for the cross-spectral density matrix of the laser beams propagating through atmospheric turbulence is derived by using the extended Huygens-Fresnel principle and the quadratic approximation of Rytov’phase structure function. And based on the definition, the analytical expressions of the spectral degree of polarization, orientation angle and degree of ellipticity of the laser beams propagating are determined. In different conditions the changes of polarization properties of completely polarized laser beams propagating through atmospheric turbulence are analyzed when the elliptically polarized Gaussian Schell-model beams and the elliptically polarized flat-topped beams are considered as completely polarized laser beams models respectively. In addition, the changes of polarization properties of completely polarized laser beams and partially polarized laser beams propagating are contrastively analyzed to further illustrate the special nature of completely polarized laser beams.The main results are listed as follows:1) Compared with the changes in the polarization properties of the partially polarized Gaussian Schell-model beams, the elliptically polarized Gaussian Schell-model beams have the advantage of the less influence by turbulence strength when they propagate through atmospheric turbulence. Likewise, by comparative analysis the elliptically polarized flat-topped beams and the partially polarized flat-topped beams, the changes in the polarization properties of the elliptically polarized flat-topped beams propagating have the advantage of the less influence of turbulence strength.2) For elliptically polarized Gaussian Schell-model beams propagating in the slant path through turbulence atmospheric, the spectral degree of polarization and the degree of ellipticity decrease first and then keep invariant with the increasing propagation distance. Besides, the orientation angle increases first and then keeps invariant with the increasing propagation distance. The same conclusion can be obtained to the elliptically polarized flat-topped beams.3) The variations of the spectral degree of polarization of the elliptically polarized Gaussian Schell-model beams propagating in the slant path through turbulence atmospheric are smaller than the partially polarized Gaussian Schell-model beams. But the variations of the orientation angle and the degree of ellipticity of the elliptically polarized Gaussian Schell-model beams propagating are larger than the partially polarized Gaussian Schell-model beams. The same conclusion can be obtained to the elliptically polarized flat-topped beams.