基于时频混合调制的高速、宽谱段、高精度广义光谱椭偏技术研究

The Spectroscopic Mueller matrix polarimetry (SMMP) can obtain the spectrum of the full elements in Mueller matrix of the sample with the advantages of non-destructive and high precision, and has wide applications in the field of the measurement of thin films and nanostructures. The existing SMMP is limited by the spectral characteristic and spectral range of the measured Mueller matrix and sensitive to Poisson noise or the wasted time in the measurement. In the paper, the existing technical merits are integrated into the time-frequency mixed modulation SMMP with only one moving part in the system. The transmission mechanism of system error, noise error and channel crosstalk error is studied and the error propagation mechanism of SMMP represented by the time-frequency mixed-modulation SMMP is clarified. The channel crosstalk suppression method, the noise error suppression method, the system parameter calibration method and the system model error correction method which can improve the measurement accuracy and the feasible scheme of time-frequency mixed modulation SMMP with high precision, wide spectrum and high data acquisition speed are obtained. The successful implementation of the project provides a novel idea and method for the research on improving the performance of the Spectroscopic Mueller matrix polarimeter, which possesses great academic value.

广义光谱椭偏技术可获取全穆勒矩阵光谱并兼具无损与高精度的优点，在薄膜和纳米结构的测量领域应用前景广泛。现有广义光谱椭偏技术存在被测穆勒矩阵光谱与测量谱段受限并对泊松噪声敏感、测量时间较长等问题。本项目将现有技术优点融合提出时频混合调制型广义光谱椭偏技术，减少系统中的运动部件并降低测量次数提高数据获取速度；研究系统误差、噪声误差以及通道串扰误差的传递机制，阐明以时频混合调制型广义光谱椭偏技术为代表的广义光谱椭偏技术误差传递机理，获得可提升测量精度的通道串扰抑制方法、噪声误差抑制方法、系统参数定标方法、系统模型误差修正方法以及实际可行的高速、宽谱段、高精度的时频混合调制型广义光谱椭偏仪原理方案。项目的成功将为提升广义光谱椭偏仪性能的研究提供新的思路与方法，具有一定的学术价值。

广义光谱椭偏技术可获取被测样品的全穆勒矩阵光谱并兼具无损与高精度的优点，在薄膜和纳米结构测量领域应用前景广泛。现有广义光谱椭偏技术存在被测穆勒矩阵光谱与测量谱段受限并对探测器噪声敏感、测量时间较长等问题。本项目将现有技术优点融合提出了一种时频混合调制型广义光谱椭偏技术，其系统中仅含一个运动部件，可在80ms内准确获取被测样品的Mueller矩阵光谱，测量绝对精度优于0.02；与现有时间调制型相比测量速度提升了5倍，与现有频率调制型相比光谱分辨率提高了至少5倍。影响测量精度的噪声误差依赖于延迟器的延迟量，固定检偏臂中旋转波片延迟量为132°，起偏臂中的延迟器快轴分别为0° 和26.5°时，噪声误差具有最小值。通道串扰的产生源于有限的通道带宽，且依赖于被测Mueller矩阵光谱的线型并与被测光谱线型的相干性呈正相关；频率通道呈等间距分布时复原Mueller矩阵元素光谱的误差最小。起偏臂和检偏臂对应的调制和解调过程相互独立，系统参数定标时可对起偏臂和检偏臂分别进行。延迟器厚度比的偏差会在光程差域的零频通道两侧引入两个通道，其距零频位置的间隔与两个延迟器厚度之差对应的光程差一致，当两个延迟器厚度之差超过0.5mm时会影响复原数据的精度；通过将起偏臂中的线起偏器旋转至正交的方向再测量一次并采用两次测量数据的加法可以消除厚度比误差引入的复原误差。本项目的研究成果可为提升广义光谱椭偏仪性能的研究提供新的思路与方法，具有一定的学术与工程价值。