光弹调制式反射差分光谱仪的理论分析

Theoretical Analysis of Reflectance Difference Spectrometer Based on Photoelastic Modulation

反射差分光谱仪是一种测量灵敏度和精度较高的研究表面/界面的新型分析仪器,但微弱的反射差分信号易受到各种噪声的干扰.作者利用Jones表示法,对光弹调制式反射差分光谱仪构建了包含器件自身缺陷和安装误差的数学模型,通过确立误差源与测量结果的联系,分析出各误差源对测量结果的影响,特别是起偏器、光弹调制器和样品的安装误差以及位相调制误差,这些系统误差经过标定可得到补偿.

Reflectance difference spectrometer （RDS） is a new type of optical analysis instrument to investigate the structures on surfaces and interfaces with high surface sensitivity and measurement precision. The reflectance difference signal from surface is normally so weak that it is easily affected by all kinds of noise during measurement, to analyze error sources is necessary to improve the performance of instrument. Here, photoelastic modulator （PEM） based RDS is introduced. And the model of the system is built in Jones matrix, where error sources are also considered. With this model, the relationships between measurement errors and error sources are established. It is shown that azimuth errors of polarizer, PEM and sample, and modulated phase error have strong influences on measurement. They should be corrected by system calibration procedure.