偏振干涉法测量晶体应力双折射精度分析

Precision analysis of polarization interference method for measuring stress birefringence of crystal

为实现晶体材料应力双折射精确测量,提出了一种以偏振干涉法为基础的测量方法,采用楔形样品避免了样品厚度可能引起的测量错误。利用椭圆偏振光理论和琼斯矩阵,推导了检偏器旋转定位精度、四分之一波片相位偏差和待测样品方位角误差对测量结果——最小可探测光程差所引入误差的解析表达式。误差分析结果表明:检偏器旋转定位精度引入的光程差测量误差最大,检偏器旋转定位精度为10′时,引入的光程差测量误差为3.1nm;待测样品方位角误差引入的光程差测量误差居中,待测样品的方位角误差为1°时,引入的光程差测量误差为0.7nm;四分之一波片相位偏差引入的光程差测量误差最小,四分之一波片的相位偏差为1.5°时,引入的光程差测量误差仅为0.1nm。

A method based on polarization interference method was proposed to precisely measure the stress birefringence of optical crystal. A sphenoid specimen was adopted to avoid measurement error caused by the thickness of specimen. Using the theory of elliptical polarized light and Jones matrix, the analytic expressions for measurement error of optical path difference caused by the rotating positional accuracy of the analyzer, the phase deviation of the quarter wave plate and the azimuth error of specimens under test were derived respectively. The results of error analysis indicate that the measurement error of optical path difference caused by the rotating positional accuracy of the analyzer is the largest, which reaches 3.1 nm when the rotating positional accuracy of the analyzer is 10＇. Besides, the measurement error of optical path difference caused by the azimuth error of the specimens under test is intermediate, which reaches 0.7 nm when the azimuth error of the specimens under test is 1° and finally the measurement error of optical path difference caused by the phase deviation of the quarter wave plate is the smallest, which reaches 0.1 nm when the phase deviation of the quarter wave plate is 1.5°.