| The electromagnetic(EM)characteristics of bianisotropic media and its internal EM waves have been widely concerned by experts and scholars.In view of the important research significance and application prospect of bianisotropic metamaterials in radio wave control,dispersion regulation and particle spin,human’s exploration of the EM characteristics of bianisotropic media has never stopped.This paper makes a preliminary theoretical study on the internal EM properties and the potential strange EM phenomena of bianisotropic media.Based on the time-harmonic plane-wave expression of Maxwell equations and the material constitutive relation,the eigenmode field and the spatial dispersion distribution of the bianisotropic media under two different observation dimensions are derived in detail by using the full-wave analysis method and starting from the spatial arrangement of the basic element structure.The spatial dispersion expression of the bianisotropic medium characterized by a given vertical magnetoelectric(ME)coupling coefficient is a transcendental equation form.Therefore,the numerical calculation will be adopted to carry out subsequent research.Its spatial distribution presents as a biquadratic distribution of a coaxial bi-ellipse.It is obtained that the biquadratic bielliptic distribution corresponds to the mode distribution of vertically polarized wave and horizontally polarized wave excitation respectively.Therefore,it is obtained that there must be the superposition of the reflection response of two polarization modes in the given bianisotropic medium,that is,double reflection.Moreover,according to phase matching,the EM phenomenon of birefringence will also appear in the bianisotropic medium characterized by the vertical coupling parameters.In order to further discuss the influence of constitutive parameters on the EM characteristics of the bianisotropic media and its internal EM waves,by keeping the values of permittivity and permeability tensor elements constant,it is found that the spatial dispersion distribution of the bianisotropic media always has four invariant wave vector points in the process of numerical regulation of ME coupling coefficient.Furthermore,the critical degeneracy conditions of the horizontal and vertical components of the wave vector are obtained according to the biquadratic dispersion distribution curve in space,and the numerical results are verified.In addition,inspired by the theory of negative refractive index materials,when the constitutive parameter of a given bianisotropic medium is set to negative,the spatial dispersion of the medium will show the mixed mode distribution of an elliptic and a hyperbola.When the value of the ME coupling coefficient increases,the intersection points of the original elliptic hyperbola spatial distribution will be pulled apart,and the gap will increase with the increase of the value.Using this property,the bianisotropic media discussed in this paper can be applied to the engineering scene of dispersion editing.Then,the EM characteristics of EM waves in the bianisotropic medium characterized by vertical ME coupling parameters are further studied,and the orthogonal phase difference between the components of EM fields in the corresponding medium is derived from the mathematical point of view,that is,the EM waves in the medium meet the condition of transverse spin of the bulk.In practical engineering applications,based on the double reflection EM characteristics of the medium and the principle of phase coherence,this paper designs a material-based reflective arbitrary polarization EM beam generation device,which has the characteristics of low profile,high degree of freedom,and low cost compared with the typical EM wave polarization control device. |
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