Changes in Stokes Parameters and Degree of Polarization of Stochastic Electromagnetic Vortex Beams on Propagation

Based on the theory of cross-spectral density matrix and the propagation laws of cross-spectral density,the general formulae were derived to calculate the generalized Stokes parameters and degree of polarization for a class of stochastic electromagnetic vortex beam while propagating in free space.Meanwhile,the influence on propagation of the generalized Stokes parameters and the degree of polarization by the coherence length was analyzed.It is shown that the higher the correlation length(the higher the degree of coherence)is,the better the vertical component can keep;the Stokes parameters and the degree of polarization increase more slowly with the increment of the correlation length increase;the generalized Stokes parameters and the degree of polarization keep almost invariant while the coherence length is much larger than beam size.