Numerical Study Of Mueller Matrix Of Random Rough Media Films

Thin film technology is a hot topic in materials science research today,among which polarisation characteristics and optical parameters are key in the process of film design and preparation,especially the rapid development of nanoscale film technology,making the study of film polarisation characteristics and optical parameters a hot issue in the field of thin film technology.At the same time,the oil film on the sea surface,as a kind of liquid medium film,is one of the main factors damaging the marine ecological environment and is a key monitoring target for all countries.Considering that Mueller matrix is an important means to explore the polarisation information of the surface of the target object,the 16 parameters it contains can completely describe the polarisation characteristics of the target surface.Therefore,this thesis numerically analyses the Mueller matrix of oil film and solid film on the sea surface,and explores the effects of incident angle,thickness and surface roughness on the Mueller matrix of media films.The specific work is as follows.1.The surface of a random rough media film was generated by the Monte Carlo Linear Filtering method,and the scattering of light waves on the rough media film was analysed using the Kirchhoff approximation,and expressions for the scattering field at any point in space above the isotropic and anisotropic media film were derived.Using the relationship between the Jones matrix and the Mueller matrix,the relationship between the 16 parameters of the Mueller matrix and the scattering coefficients is established.2.The Mueller matrices of Si₃N₄,Al₂O₃,ZnO,TiO₂ thin films on glass and silicon substrates were numerically calculated.The effects of substrate,incident angle of light wave,film thickness and film roughness on thin film Mueller matrix are analyzed.The results show that when the refractive index of the substrate is smaller than that of the thin film and when the refractive index of the substrate is greater than that of the thin film,the changing trends of the parameters of the Mueller matrix with the incident angle are quite different.When the refractive index of the substrate is closer to the refractive index of the film,the amplitude of the change of |m₀₁/m₀₀|,|m₁₀/m₀₀|,|m₂₂/m₀₀| and |m₃₃/m₀₀| with the incident angle is larger,and the variation of |m₂₃/m₀₀| and |m₃₂/m₀₀| is smaller.When the refractive index of the substrate changes,the curve of each parameter of the Mueller matrix with the thickness changes periodically like a trigonometric function,but the change trend is opposite.The variation of the surface roughness of the film does not affect the variation trend of each parameter of the Mueller matrix with the thickness.A method to characterize the thickness of single-period films by the nonlinear fitting curve of |m₂₂/m₀₀| is also proposed,which provides a new idea for the measurement and calculation of film thickness.3.Based on the A.K.Fung sea spectrum model,a two-dimensional random rough sea surface was generated,and the Mueller matrices of three types of oil films of Condensate oil,Yiyang oil and GII oil were numerically calculated.The influences of light incident angle,oil film thickness and sea surface frictional wind speed on the oil film Mueller matrix are analyzed.The results show that |m₀₁/m₀₀|,|m₁₀/m₀₀|,|m₂₃/m₀₀| and |m₃₂/m₀₀| of the three types of oil films increase first and then decrease with the increase of the incident angle,while |m₂₂/m₀₀| and |m₃₃/m₀₀| first decrease and then increase,and have a maximum value at 56°.The trend of each parameter of the three types of oil film Mueller matrices with the thickness is periodic,and the period is about 160 nm,and the smaller the oil film refractive index,the larger the peak value of each parameter of the Mueller matrix.The friction wind speed has no effect on the variation trend of each parameter of Mueller matrix with thickness.The curve of Condensate oil |m₂₂/m₀₀| varying with thickness is nonlinearly fitted,and the expression characterizing the thickness of the single-cycle oil film is obtained,which provides a reference for the estimation of the thickness of the oil film on the sea surface.