Optical Properties And The Symmetry Of Microstructure

In recent years, multiferroic materials have attracted much attention for its scientific and technologic significance. A single-phase multiferroic material is one that possesses two—or all three—of the so-called'ferroic'properties: ferroelectricity, ferromagnetism, antiferroic order and ferroelasticity. Materials without space inversion and time reversal symmetries, including the multiferroics, show a unique nonreciprocal magneto-optical effect. Broken inversion symmetry and time-reversal symmetry give rise to directional birefringence even for unpolarized light, which is nonreciprocal. Such directional birefringence is conventionally termed optical magnetoelectric effect (OME) or magnetochiral effect (MCH). The nonreciprocal optical property derived from the OME effect depends on the direction of light propagation vectork , the applied electric and magnetic fields. The dielectric function depends on whether light propagation is parallel or antiparallel to the direction of . Multiferroic materials such as GaFeO3 exhibit the spontaneous OME effect even in the absence of the external fields because multiferroic materials do not support the spatial inversion and time reversal symmetries simultaneously. Optical effects in media with broken symmetry have been of great interest from both scientific and applicational viewpoints.The purpose of this work is to study optical properties of materials without time reversal symmetry and (or) spatial inversion symmetry. The main results of our study are listed as follows.I. The study of the controlled magneto-optical effect in one-dimensional magnetophotonic crystalAn electrically controllable Kerr effect in magnetophotonic crystal consisting of magnetic materials and nematic liquid crystals is showed based on the properties of nematic liquid crystals. First, we treat nematic liquid crystal as a homogeneous isotropic dielectric layer approximately. Numerical results show that Kerr effect is changed remarkably by adjusting the permittivity of liquid crystal, and the maximum value of kerr rotation angle becomes large as the permittivity of liquid crystal increases. Such properties demonstrate the possibility of tunable magneto-optical devices based on nematic liquid crystal. It offers a new scheme to realize the tunable magneto-optical effect. Because of its simplicity and effectiveness, our model can offer a good theoretical basis for experiments in tunable magneto-optical effect. Furthermore, we investigate the tunable negative refraction of the ferromagnetic nanowires composite.II. The study of optical magnetoelectric effect with moving mediaWe report a theoretical investigation of the possibility of realizing the optical magnetoelectric effect with a moving medium. The movement of the medium can develop the anisotropic electromagnetic environment; therefore, it will bring about the cross-coupling term between the electric displacement vector and magnetic induction in the rest frame of the laboratory. We may call the cross-coupling term in a moving media"pseudomagnetoelectric effect,"which will lead to optical magnetoelectric effect directly. This unique approach is quite distinct from other methods using conventional multiferroic materials or artificial materials with broken space inversion and time reversal symmetries simultaneously. Its advantage lies in the controllability of the optical properties, which change with the change of velocity and intrinsic refractive index of the moving medium. This work in the present frame offers a route to tune this phenomenon.Ⅲ. The study of directional anisotropic optical effect in magnetophotonic crystalPolarization-independent directional anisotropic optical effect in one dimensional magnetophotonic crystals consisting of ferromagnetic materials and anisotropic dielectric layers with misaligned in-plain anisotropy is investigated. We have known that such a configuration do not support time reversal and space inversion symmetries simultaneously. The existence of the directional anisotropic optical effect is examined according to Muller matrix method based on the asymmetric properties of the system. Our results show that this effect can be realized in such magnetophotonic crystals without the presence of the multiferroic materials. And the directional anisotropic optical effect has directional anisotropy which depends on whether the wave propagates from the left or right side of the magnetophotonic crystal. Furthermore, the order of magnitude of this unique electromagnetic effect can be up to 10?3 . We expect that our results could be useful for the design of polarization-independent devices based on magnetophotonic crystals.