Modeling And Simulation Of Scattering Medium Of Non-Spherical Particles Based On Vector Monte Carlo Algorithm

The transmission of polarized light in turbid media will change its polarization state and bring rich polarization information,which is the key to realize all kinds of polarization technology.Therefore,it is of great significance to study the multiple scattering characteristics of polarized light in turbid media.Through simulation experiments and related literatures,it is found that the relative size between particle and wavelength of incident light will be different in the single scattering characteristics,and the single scattering characteristics of particles with different shapes will also be different.In order to further study the effect of particle shapes on the multiple scattering transmission characteristics of polarized light,according to the relationship between the radius of spherical particles or the equivalent spherical radius of non-spherical particles and the wavelength of incident light,the scattering particles are divided into Rayleigh scattering particles and Mie scattering particles.Then,the polarization maintaining ability of circularly polarized light and linearly polarized light is studied qualitatively and quantitatively in the media satisfying Rayleigh scattering and Mie scattering respectively.For the previous method based on the accurate solution of the Mie scattering theory and the Monte Carlo method can only calculate the transmission of polarized light in spherical particle media,the method of combining the Tmatrix and the Monte Carlo algorithm is used in this paper,which can not only calculate the multiple scattering transmission of spherical particles,but the calculation of non-spherical particles.The specific contents are as follows:(1)Based on the T-matrix method,the single scattering characteristics of symmetric non-spherical particles such as ellipsoid,finite length cylinder and Chebyshev shape are calculated,and the relationship between the elements of the single scattering Mueller matrix and the scattering angle is made into a sampling table,so that the random sampling of scattering angle and azimuth angle can be carried out in the subsequent vector Monte Carlo method.(2)A medium model containing randomly oriented rotationally symmetric nonspherical particles is established.Stokes vector is used to represent the polarization state of the photons.Based on the vector Monte Carlo algorithm,statistical random sampling of the single-scattered Mueller matrix elements of the particles is performed to obtain the photon scattering angle and azimuth angle.And through two simulation experiments to verify the rationality of the method and the correctness of the model.(3)Based on the superposition of Stokes vectors,the polarization-maintaining ability of circularly polarized light and linearly polarized light after multiple scattering and transmission is qualitatively and quantitatively studied in Rayleigh scattering and Mie scattering,respectively.It is found that the shape of the particles has little effect on the polarization maintaining ability of the Rayleigh scattering particle medium,but has a significant effect on the polarization maintaining ability of the Mie scattering particle medium.(4)By counting the backscattered photons of the Mie scattering medium,it is found that in the Mie scattering particle medium,the difference in particle shape has a significant effect on the spatial distribution of the intensity of the backscattered polarized light and the spatial distribution of the degree of polarization.