Propagation Characteristics Of Electromagnetic Wave In Chiral Medium And Light Scattering Of Plane Wave By Chiral Particles

Chirality is a geometric notion which refers to the handedness of an object that two objects look almost exactly alike.But they cannot be brought into congruence with its mirror image by translation and rotation.Chiral media exhibit a number of unique optical phenomena such as rotation of the plane of polarization,circular dichroism,and others.Due to these fascinating properties,chiral media have been widely studied and applied in diverse areas such as Physics,Chemistry,Medical Biology,metamaterial detection,and metamaterials fabrication.In this dissertation,the optical properties of isotropic chiral media and electromagnetic scattering of chiral media are studied in detail based on the electromagnetic field theory.The derivation of the relationship between medium parameters are given based on the chiral constitutive equations,influences of chiral parameters on the propagation modes of electromagnetic waves are studied,the formulas of reflected and transmitted powers from a chiral-chiral interface,and those from a chiral-achiral interface are derived,light scattering by a large-sized chiral particle illuminated by a polarized incident plane wave is investigated.The main work and results are as follows:Firstly,a Geometrical Optics Approximation(GOA)method is introduced for the computation of the light scattering of an absorbing spherical particle illuminated by a linearly polarized electromagnetic wave.The effective refractive index,the complex refractive index and the phase shift which are different from the case of transparent particles are given.The relationship between the scattering angle and the incident angle is studied.Numerical results obtained by the GOA method are in good agreement with those obtained by the Lorenz-Mie theory(LMT),which validates the GOA method for large particles.Then,a brief introduction is presented to the basic principles of the generalized Lorenz-Mie theory(GLMT),the vectorial complex ray model(VCRM),and the LMT.Four different sets of constitutive relations about the characterization of chiral media are presented.Using both Maxwell equations and constitutive relations for a chiral medium,propagation equation of an electromagnetic wave in the chiral medium is deduced,and the relationship between material parameters is then derived.Characteristics of an electromagnetic wave propagation in the isotropic chiral medium(ICM)are discussed on the basis of the Post-Jaggard constructive equations and the Maxwell equations,the formulas of reflection and transmission matrix coefficients are obtained,as well as that of the reflected and transmitted power coefficients.Derivation of the reflection and transmission coefficients is given as the chiral medium 1 or 2 reducing to an anchiral medium.Electromagnetic wave reflection and transmission at an isorefractive chiral media interface,at a cross-refractive chiral media interface,at a mirror-Conjugate Chiral Media interface,and at the surface of a perfect electromagnetic conductor are discussed.Effects of the incidence angle on the variation of propagation modes and reflection and transmission characteristics are investigated in detail.Propagation properties of an arbitrarily polarized electromagnetic wave through a chiral medium is presented.Effects of the chiral admittance parameter on the propagation modes of the plane wave traveling in a chiral medium are investigated.Based on the continuity condition of normal component of the time-averaged Poynting vectors across a planar interface between an isotropic achiral medium(IAM)and an isotropic chiral medium(ICM)for the incident,the reflected,and the transmitted waves,theoretical formulas are derived for the normalized reflection and transmission powers from an IAM-ICM interface for an arbitrary polarized incident wave,and those at an ICM-IAM interface for right-hand circularly polarized(RCP)or left-hand circularly polarized(LCP)incident wave are obtained as well.The behavior of the reflected and transmitted waves for three different cases including impedance matching is studied,and effects of incidence angle,chiral parameter,and permittivity on the power reflection and transmission coefficients are investigated in detail.The GOA method is extended to the forward light scattering of a large-sized ICM spherical particle illuminated by a polarized plane wave.The reflection and transmission Fresnel coefficients at the surface of a chiral sphere are revisited on the basis of the continuity condition of the tangential components of the electromagnetic field.Expressions of the scattering fields are derived by a combination of the amplitudes of the externally reflected,the directly refracted,and the diffracted waves,where effects of polarization and the phase shift due to total reflection are taken into considered.Numerical results of co-polarized and cross-polarized scattering intensity distributions of a large-sized ICM sphere are presented.Effects of chiral parameter,permittivity,and size parameter of the sphere on the scattering patterns are investigated in detail.The GOA method is also extended to the study of light scattering by nonspherical chiral particles illuminated by a plane electromagnetic wave.Procedures for accurate ray tracing in chiral cylinder and ellipsoid models are presented in detail.Recursive relations for the incident angle,the coordinates and the length of each optical path between two successive internal reflection points of the ellipsoid model are derived.The phase shifts caused by the focal line and optical path under the two models are analyzed,and expressions of the scattering fields are presented as well.Numerical results of the dimensionless scattering intensity for the forward light scattering are given.Light scattering by a chiral sphere near surface of an achiral medium is studied.The reflection and transmission coefficients are derived from the expansion of vector wave functions of the incident,the reflected and the transmitted waves.With the expanded spherical vector wave functions of the incident wave,the internal field,the scattered field,and the reflected scattered field of the chiral sphere,expressions of expansion coefficients and each field component are obtained by using a projection method.Numerical results of the normalized differential cross section distributions of TE and TM plane waves are displayed.