随机电磁涡旋光束传输过程中斯托克斯参量和偏振度的变化

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

基于交叉谱密度矩阵理论及其传输规律,推导随机电磁涡旋光束在自由空间中传输时的广义斯托克斯参量和偏振度的公式,分析相干长度对广义斯托克斯参量和偏振度的影响.研究结果表明:相干长度越长,即相干度越高,光束的涡旋特性越容易保持;随着相干长度的增加,斯托克斯参量和偏振度增加的比较缓慢;当相干长度远大于光斑尺寸时,广义斯托克斯参量和偏振度基本保持不变.

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.