针对双波片偏振调控结构,基于Stokes-Mueller矩阵偏振算法,对双1/4波片和双1/2波片的偏振调控机理作了详尽的理论分析,得出调控偏振态与双波片快轴方向之间的关系,并追迹其在庞加莱球上的运动轨迹.基于双波片调控结构搭建偏振测量系统,根据入射和出射Stokes矢量构建了投影关系矩阵算法,完成了待测元件Mueller矩阵的测量,并分析了波片的快轴方向误差和位相延迟误差对Mueller矩阵测量结果以及对出射偏振态调控精度的影响.分析结果表明:波片的快轴方向误差控制在±2°内,位相延迟误差不大于λ/300时,Mueller矩阵的最大测量误差为0.040 2,波片自身误差对测量结果的影响可以忽略不计;波片自身误差所引起的方位角误差不大于0.16rad时,快轴方向误差引起的椭率角误差最大不超过0.032 rad,位相延迟误差导致的椭率角误差小于0.015 rad,且对偏振度无影响.
Based on the Stokes-Mueller matrix polarization algorithm, the polarization control mecha- nism of a biplate that consists of double quarter wave-plates or double half wave-plates was analyzed in detail. We have derived the analytical relations between the modulated polarization state and the fast- axis direction for the biplate. The movement trajectory of modulated polarization state on the Poincar6 sphere was obtained. Which helps us to propose a polarization control measurement system using a bi- plate to complete the measurement of the Mueller matrix based on the projection matrix algorithm for the incident and exiting Stokes vectors. The polarization control accuracy for the exiting Stokes vector was also analysed. For a biplate that the error along the fast axis direction is ~ 2 o and the retardance er- ror is k/300, the maximum measurement error of Mueller matrix is 0. 040 2. When the azimuth error caused by the error of the biplate is less than 0.16 rad, the elliptic angle error caused by the fast axis direction is not more than 0. 032 rad, the ellipsometry error caused by the retardance is less than 0. 015 rad, and it has no influence on the degree of polarization.