用于红外晶体双折射测量的单1/4波片法

Senamont based measuring method for birefringence of infrared crystal

提出了一种基于单1/4波片法的测量方法以实现红外波段光学晶体双折射光程差的精确测量。采用厚度差小于一个周期厚度的两个样品进行比对,有效克服了单1/4波片法测量厚度的限制。依照此原理研制了测试波长为3.39μm的晶体双折射测试设备。应用琼斯矩阵理论,推导了存在主要误差因素时的信号光强解析表达式,并由此分析了起偏器方位角误差、1/4波片定位精度、样品方位角偏差、检偏器旋转定位精度对测量结果的影响,综合评价了本测量方法的精度。实验结果表明,应用研制的设备实测标准1/4波片的双折射光程差误差为0.003 76μm,相对误差为0.44%,满足系统要求。得到的结果表明,采用基于单1/4波片法的新测量方法能够有效、精确测得红外晶体的双折射光程差。

Abstract： A method based on the Senamont method was proposed to precisely measure the birefringence of an infrared crystal. Two specimens with the Optical Pass Differences （OPD） within 1 wave- length caused by the birefringence were compared to overcome the measured OPD limit of Senamont method and to extend the method to the infrared band. According to the new method, a set of appara- tus for measuring the birefringence of infrared crystal was developed. Moreover, by applying the Jones matrix, the expressions of signal intensity with various error sources were proposed to analyze precisely the influences of the error sources including the azimuth error of a polarizer, the orientation error of the quarter wave plate, the azimuth error of the specimen and the orientation error of the analyzer, then the measuring precision of this method was evaluated. The experiment results indicate that the measured OPD error for a standard quarter wave plate is 0. 00376 um, and the relative error is 0.44 %, which is within the precision and satisfies the system targets.