Vectorial Complex Ray Model In Light Scattering Of A Small Sphere

Small particles of various shapes widely exist in nature and industrial process, and the measurement of their parameters(shape, density, refractive index, size distribution, etc) is of practical significance on environmental monitoring, production controlling, and energy consumption. Light scattering by a small particle is a theoretical foundation of particle sizing. Compared with Mie theory, which rigorously solves the interaction of light scattering by a regular particle, geometrical optics has the advantage of speed for the case of large particles. In Vectorial Complex Ray Model(VCRM) proposed recent years, vectorial Fresnel formula is introduced, and curvatures of wavefront and dioptical surface are used to calculate local divergence factors and to determine the phase shift due to the focal lines. VCRM has potential for light scattering by particles of irregular shape. In this paper, VCRM is applied to light scattering by a concentric coated particle, and the propagation of rays in an uniaxial anisotropic particle combined with the non-coordinate approach.In the paper, VCRM is first employed to the scattering of coated sphere. A binary code is proposed to represent a ray-tracing mode, which uniquely corresponds to every physical process and has a simple mathematical form for code. A vectorial ray-tracing expression is derived to easily locate the spots, where rays encounter the interface of a coated sphere. Base on VCRM, we can avoid the complicated derivation and calculation of angles in traditional geometrical optics method, and can consider the contributions of high-order rays. Numerical results are compared with rigorous results, and a good agreement is obtained.Since rigorous theories face difficulties for the scattering by a large anisotropic particle, geometrical-optics is employed to solve the scattering of anisotropic spheres. Combined with non-coordinate approach, the reflection/refraction coefficient is derived when light incidents from anisotropic media to isotropic media in arbitrary optical axis orientation. Such coefficients are verified by the comparison with that for isotropic case. The calculations of optical path and divergence factors in anisotropic media are finally discussed.