Research On Mid-Infrared Mueller Matrix Spectroscopic Ellipsometer

Infrared materials are widely used in solid physics,molecular chemistry,thin film growth,biomedicine and national defense,and their optical constants are important for their function and performance.As a non-destructive,high-precision,high-sensitivity measurement method,the infrared ellipsometer can realize the rapid characterization of the optical constants of the materials in the infrared wide spectrum.It can obtain information such as phonon vibration,free carrier migration and molecular vibration,so it is widely used in the characterization of infrared thin film materials.The infrared Mueller matrix ellipsometer can obtain all the Mueller matrix elements of the sample in one measurement process,thus showing great advantages in the characterization of anisotropic infrared materials.This thesis focuses on the research on Fourier transform mid-infrared Mueller matrix ellipsometer.The main research work and innovations include:Firstly,according to the measurement requirements of infrared anisotropic thin film materials and the research status of mid-infrared Mueller matrix ellipsometer,a Fourier transform mid-infrared Mueller matrix ellipsometer is proposed.The design of the achromatic retarder and the high extinction ratio polarizer is proposed.Secondly,the Fourier transform mid-infrared Mueller matrix ellipsometer system model is established.The conditional number is used to optimize the system configuration matrix of stepped polarization modulation to reduce the error transmission,and a calibration method suitable for the instrument is proposed.The feasibility and correctness of the system model,optimization results and calibration methods are verified by simulation experiments.Thirdly,the instrument optical system design,instrument structure and control system design were completed.Achromatic phase retarder for mid-infrared is designed,and the high extinction ratio of polarizer is realized by using bimetal wire-grid polarizer.The design of the instrument optical system,instrument structure and control system are completed.The achromatic phase retarder based on the principle of total reflection phase change in the mid-infrared band is designed.High extinction ratio of polarizer achieved by wire grid bi-polarizer scheme.Finally,the construction of the Fourier transform mid-infrared Mueller matrix ellipsometer was completed,and the air and silica standard film samples were measured using the built instrument.16 quantities of a Mueller matrix of thin film samples were measured at the spectral range of 1.5-5.5 um.The single point measurement time is 3 minutes.The Mueller matrix element has an accuracy of ±0.06.