弹光和电光级联的组合相位调制型椭偏测量术

利用弹光调制器的偏振调制优势,提出了将弹光调制器和电光调制器级联的组合相位调制型椭偏测量术。该技术采用单光路实现信号探测,通过切换电光调制器的两个工作状态,并结合数字锁相信号处理技术来完成样品反射光的p分量和s分量的幅值比Ψ和相位差Δ的全范围高精度测量。对提出的新型椭偏测量原理进行了分析,搭建了相应的实验系统。完成了弹光调制器的调制电压峰峰值和相位调制幅值关系的定标,定标结果优于99.05%,然后还采用系统初始偏移值的方法对实验系统进行了校准。最后,运用该系统对石英玻璃反射样品进行了实验分析,得到的Ψ和Δ的测量精度分别优于0.08°和0.81°。实验结果显示系统校准有效地消除了电光调制器和弹光调制器的剩余双折射引入的测量误差;数据采集和处理时间均在ms量级。提出的测量技术具有宽光谱测量、工作稳定、重复度高、测量速率快、成本相对较低和系统便于工业自动化集成的潜在优势。

Phase-modulated ellipsometry combined photo-elastic modulation with electro-optic modulation

On the basis of the advantages of photo-elastic modulation, a phase-modulated ellipsometry combined a photo-elastic modulator with an electro-optic modulator is proposed. It uses one single detection light path to obtain the signals.By switching two work conditions of the electro-optic modulator,it takes lock-in signal processing technology to solve out the two ellipsometric parameters, amplitude ratio Ψ and phase difference Δ, from the p component and s component of reflection light of a simple. The principle of the new type of ellipsometry is analyzed, and a principle prototype is set up. The relationship between the peak value of modulated voltage and the phase modulation amplitude of the photo-elastic modulator is calibrated, and the calibration result is better than 99.95%. Then, an instrument offset method is used to calibrate the experimental system. Finally, a quartz glass reflective sample is analyzed by using this system, and the measurement accuracy of the Ψ and Δ are respectively better than 0.08° and 0.81°. The experimental results show that the instrument offset method effectively eliminates the detection errors introduced by the residual birefringence of the photo-elastic modulator and electro-optic modulator, and the data acquisition time and signals processing time are in the order of the millisecond. In conclusion, this phase-modulated ellipsometry proposed has potential advantages of wide spectrum measurement, stable operation, high repetition rate, fast measurement speed, low cost, and is conducive to industrial automation integration.