Research On Some Key Problems In Optical Characterization Of Optical Coatings

The measurement of optical characteristics of thin film plays an important role in the preparation of thin-film device with high performance.The development of technology makes the preparation of complicated optical thin films become possible, and the designed films should be under a series of characteristics evaluation before applied into practice,which can in turn serve and modify the current design.The research is focus on some key problems about the measurement and calculation of various optical characteristics of thin film,and the main content are as follows:1,Measurement of photometric property of optical thin film.After the advantage and limitation of current spectrometer are analyzed,a novel design of system for measuring both spectra transmittance and reflectance is developed. Compared with others,some new features are appended in our design such as processing method of oblique incidence,measurement of muti-angle reflectance, measurement of temperature drift,measurement and automatic calibration of polarization and Data collection system with high precision.The test results are also given to prove validity and feasibility of our system.A series of experiments are carried out both in our new system and Hitacl(l|¨) UV-3100 to perform Precision Analysis.The source and solution of the error are also discussed.2,Determination of optical constants of optical thin film.Several methods about determination of the optical constants of optical thin film are discussed.The spectral fitting method,especailly combining with optimization algorithm such as simplex method,Simulated Annealing method and genetic algorithm is implemented with code.Both advantages and limitations are discussed for all these optimization algorithms,and the validity of the method is verified through both simulation and experiment.To overcome the shortcoming of each optimization algorithm,the assumption of hybrid algorithm is also mentioned.Since the fact that the error during the spectral Spectrum Test cannot be reduced to zero,the way to weaken its effect by wavelength selection is investigated.3,Measurement of phase information of optical thin film.The system of white light interferometer is set up to retrieve phase information including GD(group delay) and GDD(group dispersion delay) combining with various algorithms(Fourier transformation method,node method,wavelet transformation method and so on) with high precision.A series of experiments are carried out and the test results are compared with theory to verify the validity of the phase-retrieve system and method mentioned above.The effect of the scale change of the smooth window to the test result is discussed.Besides,considering the noise level during phase measurement, both the sources of error and their corresponding sulotion are discussed.