随机涡旋光束在生物组织传输中偏振态的变化

Changes of the polarization states of random optic vortex beams propagating in biological tissues

基于广义惠更斯-菲涅尔原理,推导出随机高斯-谢尔模型(GSM)涡旋光束在生物组织中交叉谱密度矩阵元的解析表达式,并用以研究了随机GSM涡旋光束在生物组织传输中的偏振态变化。详细研究了生物组织折射率结构常数C2n、光束波长λ、空间相关长度σyy和传输距离z对偏振度P、方位角θ和椭圆率ε变化的影响。研究表明,λ=10μm的远红外光束在人体表皮组织传输中P、θ和ε的值在一段传输距离内几乎不变;λ=0.325μm的紫外光在传输中,ε的值急剧减小。随着z的增大,C2n越大,即生物组织湍流越强,P值越小,θ绝对值越大,ε值越大;当z足够大,P、θ和ε在不同生物组织传输中的值分别趋于一定值。此外,P、θ和ε曲线变化和σyy与σxx的相对大小有关。

Based on the extended Huygens-Fresnel principle,the analytical expressions of the cross-spectral density matrix elements for random electromagnetic Gaussi an Schell-model （GSM） vortex beam propagating in biological tissues are derived a nd used to study the changes in its polarization state.The detailed investigatio n includes the influence of the structure constant of the refractive-index of biological tissu es Cn^2, beam parameters （λ and σyy） and propagation distance z on the changes in the deg ree of polarization P,the orientation angle θ and the ellipticity ε.It is shown that the val ues of P,θ and ε are almost un changed at a length of propagation distance for the far infrared beams （λ=10μm） propagating through the biolo gical tissues.The value of ε decreases quickly for ultr aviolet beam （λ=0.325μm）.With increasing the propaga tion distance z,the bigger Cn^2 is,the stronger the biological tissue turbulence is,the smaller the value of P is,the bigger the absolute value of θ is,and the bigger the value of ε is.When the propagation distance is sufficiently long ,the values of P,θ and ε tend to a constant in different biological tissues,respectively.Besides, the curve changes of P,θ and ε are also related to the relative magnitude between σyy and σxx.