Cai Wei, Ni Xiaohui, Gayen S K, Alfano R R
Institute for Ultrafast Spectroscopy and Lasers, Department of Physics, The City College of City University of New York, New York, NY 10031, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Nov;74(5 Pt 2):056605. doi: 10.1103/PhysRevE.74.056605. Epub 2006 Nov 8.
The backscattering of circularly polarized light pulses from an infinite uniform scattering medium is studied as a function of helicity of the incident light and size of scatterers in the medium. The approach considers a polarized short pulse of light incident on the scattering medium, and uses an analytical cumulant solution of the vector radiative transfer equation with the phase matrix obtained from the Mie theory to calculate the temporal profile of scattered polarized photons for any position and any angle of detection. The general expression for the scattered photon distribution function is an expansion in spatial cumulants up to an arbitrary high order. Truncating the expansion at the second-order cumulant, a Gaussian analytical approximate expression for the temporal profile of scattered polarized photons is obtained, whose average center position and half width are always exact. The components of scattered light copolarized and cross polarized with that of the incident light can be calculated and used for determining the degree of polarization of the scattered light. The results show that circularly polarized light of the same helicity dominates the backscattered signal when scatterer size is larger than the wavelength of light. For the scatterers smaller than the wavelength, the light of opposite helicity makes the dominant contribution to the backscattered signal. The theoretical estimates are in good agreement with our experimental results.
研究了来自无限均匀散射介质的圆偏振光脉冲的后向散射，作为入射光的螺旋度和介质中散射体尺寸的函数。该方法考虑了入射到散射介质上的偏振短光脉冲，并使用矢量辐射传输方程的解析累积量解以及从米氏理论获得的相位矩阵，来计算在任何检测位置和任何检测角度下散射偏振光子的时间分布。散射光子分布函数的一般表达式是空间累积量的展开式，可达到任意高阶。在二阶累积量处截断展开式，得到了散射偏振光子时间分布的高斯解析近似表达式，其平均中心位置和半高宽总是精确的。可以计算与入射光共偏振和交叉偏振的散射光分量，并用于确定散射光的偏振度。结果表明，当散射体尺寸大于光的波长时，相同螺旋度的圆偏振光主导后向散射信号。对于小于波长的散射体，相反螺旋度的光对后向散射信号起主要作用。理论估计与我们的实验结果吻合良好。
