Research On Development And Application Of The Photoelastic-modulated High-speed Mueller Matrix Ellipsometer

In the rapid dynamic physicochemical reaction processes,such as particle migration,molecular self-assembly,orientation ordering of liquid crystal molecules under external electric field,local physical properties and microstructure are changed at the same time,which often occur in millisecond or even microsecond time scale.Due to the complexity and instantaneity of rapid dynamic process,the related real-time and in-situ metrology are faced with severe challenges.Focusing on the goal of rapid dynamic process measurement,a high-speed Mueller matrix ellipsometer(MME)based on the principle of photoelastic modulator(PEM)polarization modulation and division-of-amplitude polarization demodulation is developed in this dissertation.The self-developed photoelastic-modulated MME(PMME)not only has the advantages of high accuracy and precision of traditional MME,but also can realize full Mueller matrix measurement with microsecond temporal resolution.With the characteristics of high measurement accuracy and temporal resolution,the PMME shows a great application potential in the real-time measurement of rapid dynamic process.The main research work and innovations of the dissertation include:The measurement principle based on PEM polarization modulation and division-ofamplitude polarization demodulation are proposed.Meanwhile,the Mueller solution system model based on the nonlinear regression iterative light intensity fitting algorithm is established,with which the fast and high accuracy measurement of the full Mueller matrix is realized.Besides,the error transfer model of PMME has been established based on the established system model,and the error sources,classification and transfer process are analyzed systematically.Through different types of error transfer simulation experiments,the influence of various errors on the measurement accuracy of Mueller matrix and the extraction accuracy of optical parameters is evaluated,and the correctness of the error transfer model is verified.To reduce the error in the measurement of Mueller matrix caused by polarization distortion in the beam splitter,a characterization model of beam splitter based on polar decomposition of Mueller matrix and the corresponding parameterized in-situ calibration method are proposed,with which the polarization distortion in the beam splitter is compensated,and the accurate calibration of the polarizing matrix is realized.Meanwhile,the calibration method of PEM based on discrete Fourier transform algorithm and Bessel function expansion is proposed.With the proposed in-situ calibration method,the dynamic modulation characteristics of PEM under different driving voltages are obtained.Besides,to minimize the influence of system error and random error on the measurement of Mueller matrix,the multi-objective optimization method based on genetic algorithm is used to find the optimal system measurement configuration.And the simulation results show that the accuracy and robustness of the instrument are significantly improved under the optimal measurement configuration.Then,a PMME with high precision and high temporal resolution is designed and developed,and the problem of optical path design,control system design and mechanical structure design are solved at the same time.Through the measurement experiments of different types of samples,the measurement performance evaluation of the instrument is completed,and the results of performance evaluation show that the measurement error of Muller matrix elements is less than 0.005,the repeatability measurement variance is within0.003,and the measurement temporal resolution is up to 3μs,which meets the requirements of real-time in-situ measurement of rapid dynamic physicochemical process.Finally,with the self-developed instrument,the application research on the dynamic modulation characteristics of nematic liquid crystal variable retarders(LCVR)and the realtime attitude tracking of free-moving object are carried out.In the apllication reaserch,the dynamic optical characterization model of sample based on Mueller matrix formalism is established,and the extraction method of dynamic optical parameters in the measurement of rapid dynamic process is also proposed,with which the high-precision,in-situ and realtime monitoring of complex and changeable rapid dynamic process can be realized.The application results show that the self-developed instrument has excellent measurement performance and potential application prospects in real-time in-situ measurement of rapid dynamic process.