Negative Refraction And Beam Shift In The Metamateirals With Anisotropy Or Chirality

Metamaterials are referred to as the composite material with artificial preparation,which exhibit superior physical properties not observed in the nature materials. Andelectromagnetic metamaterials have great potential for modulating the optoelectronicinformation and existing technical limitations can be broken through due to the novelphysical phenomena and mechanism. At this point, the preparation, optical characteristicsand application of the metamaterials are currently the research hotspot. In this thesis, wemainly aim at the realization and the optical characteristics of the metamatials, the negativerefraction and the beam deflection effect of the anisotropic and chiral metamaterials areinvestigated. The major contents and most important results of our work are listed asfollows:1. Modulating the effective negative refraction in anisotropic layeredcompositesThe negative refraction of an anisotropic metamaterial has been investigated innumerous literatures, but for the composite system, it has not explicity given about how tomodulate the negative refraction by the volume fraction of the inclusion, the incidentfrequency and other parameters. In this regard, we investigate the characteristics ofelectromagnetic wave propagation in a two-component layered structure composed ofalternating isotropic metal material and anisotropic magnetic material. With transfer matrixmethod, effective permittivity and permeability tensors of the composite system arederived in the limit of long wavelength. For realizing the quasi-left-handed material withnegative refractive index, i.e., the absolute quasi-left-handed material, the influence of thevolume fraction of the magnetic material, the angle of incidence and the incident frequency are discussed. Numerical results show that for a given volume fraction of the magneticmaterial, the composite system behaves as an absolute quasi-left-handed material in acertain frequency region, and there exists an optimal volume fraction, at which the absolutequasi-left-handed frequency region has a maximal width. Moreover, the transition betweenpositive and negative index takes place by the adjustment of the incident frequency.2. Lateral shift of the reflected wave through an uniaxial anisotropicmetamaterialFor the lateral shifts in the anisotropic metamaterial, the results of some researcheshave been shown that the lateral shifts will be affected by the electromagnetic parametersof anisotropic materials, the absorption of the material, the thickness of the slab and theangle of incidence. But in their studies, the electromagnetic parameters are not chosenfrom the actual material, and can not be modulated. However, the preparation of theanisotropic metamtereial containing parallel metallic nanowires has already been done inexperiment, which can exhibit negative refraction. Then we proceed from actual materials,consider a semi-infinite anisotropic metamaterial system consisting of aligned metallicnanowires in a dielectric matrix, and the lateral (Goos–H nchen, GH) shift of atransverse-magnetic (TM) wave reflected from the metamaterial is investigated. Based onBruggeman effective medium theory, we obtain the electromagnetic parameters conditionsfor realizing the negative refraction, which are dependent on both the incident wavelengthλ and the volume fraction of metallic inclusions f. The results show that the metamaterialwith positive or negative refraction can be obtained by suitable adjustment of λ and f. Nextthe expression of GH shift of the reflected beam is obtained with the stationary-phasemethod, and the influences of λ and f on the GH shift are discussed. It is shown that in thecase of weakly absorption, the GH shift can be enhanced near the pseudo-Brewster angle.Meanwhile, the transition from negative GH shift to the positive one can be realized byadjusting λ for the positive metamatrial, while the transition from positive GH shift to thenegative one can be realized by adjusting f for the positive metamatrial. As the absorptionis large, the GH shift will be enhanced at the close-to-grazing incidence. Numericalsimulations are performed for a Gaussian-shaped beam and the validity of the stationary-phase approach is demonstrated. In the end, by using COMSOL simulation, acomprehensive understanding is given and the above analysis is confirmed.3. Lateral shifts near pseudo-Brewster dip on reflection from a chiralmetamateria slabThe research for the general metamaterial shows the GH shifts will be greatly affectedby the parameters, such as the absorption of the material, the thickness of the slab, and theangle of incidence. And for the chiral metamaterial, the GH shift is investigated only byconsidering the chiral interface and without absorption. In fact, it is more meaningful tostudy the GH shifts from a chrial metamaterial slab of lossy. The reflection andtransmission characteristic of arbitrarily polarized incident beam in chiral metamaterialslab are derived firstly. On the basis of angular spectrum representation, the formalismwith both perpendicular and parallel components of the reflected field is established tostudy the lateral (GH) shifts from a chiral slab of lossy for the transverse electric(TE)-polarized incident wave. By comparing the GH shifts in the negative and positivechiral metamaterial, the GH shifts can be enhanced near the pseudo-Brewster angle forboth the perpendicular and parallel components of the reflected beam, and the behavior ofthe GH shifts for a negative chiral slab is opposite to that for a positive chiral slab. For thenegative chiral slab, it also shows that the enhanced GH shifts with positive or negativevalue and the number of the enhanced peak can be adjusted by the chirality parameter forboth the perpendicular and parallel components of the reflected beam. Meanwhile, theinfluence of the thickness of the chiral slab on the GH shifts is also dependent on the angleof incidence. Moreover, in the presence of inevitable loss of the chiral slab, the enhancedlateral shifts will be decreased, and the pseudo-Brewster angle will disappearcorrespondingly. In the end, numerical simulation of a Gaussian-shaped beam shows thatthe wider the incident beams are, the smaller the discrepancy is. 4. Spin Hall Effect and spin-dependent split of light beam in a chiralmetamaterial slabSince the essence of the Spin Hall Effect of light (SHEL) is the transverse (IF) shift,and special attention to the SHEL of the centers of the refrlected and refracted beams forthe chiral metamterial is paid. Then, the spin Hall Effect of light (SHEL) for the chiralmetamaterial slab is investigated by analyzing the spatial transverse shifts (TSs) of the twospin-dependent components of the reflected beam. A propagation model is establishedbased on the angular spectrum representation, and the expression is given to describe theIF shifts of the reflected beams composed of two circularly polarized components. Theinfluences of the parameters of the chiral slab and the polarization of the incident beam arediscussed. The results show that the two spin-dependent components are asymmetric dueto caused by SHEL, the positive and negative values of the transverse shifts of the twocomponents can be modulated near the pseudo Brewster angle by adjusting the angle ofincidence, and the SHEL can be enhanced or suppressed. Meanwhile, by adjusting theparameters of the chiral slab, such as the chirality parameterκ and the thickness of theslab d, the SHEL can be enhanced and the splitting of the two components. We also findthe SHEL exists in the chiral metamaterial for the special linear polarization (TE and TM)of the incident beam, which is not found in a general material. Moreover, the largenegative or positive IF shifts and the transition between them can be obtained by theadjustment of the polarization of the incident beam and the splitting of the twospin-dependent components can be obtained. It means that an opportunity will be providedto realize and control the transverse splitting of the light for the chiral metamaterial.