磁电耦合超材料本构矩阵获取方法的研究

单负(仅介电常数或仅磁导率小于零)超材料以及由导线-开口谐振环组成的双负超材料本构参数的提取通常采用传统的S参数方法. 由于磁电耦合超材料存在交叉极化现象, 仅用介电常数和磁导率两个本构参数无法准确描述其电磁特性. 传统的S参数提取方法一开始就假定超材料仅具有介电常数和磁导率两个本构参数, 所以采用该方法提取磁电耦合超材料本构参数存在明显局限性. 将磁电耦合超材料中的电元件和磁元件分别等效为面电流和面磁流, 通过推导平均电通密度和磁通密度与外加电磁场的相互关系, 从理论上获取了磁电耦合超材料2×2 的本构参数矩阵, 确定了磁电耦合超材料这四个本构参数与磁元件的磁导率、电元件的介电常数、空间色散项和耦合系数之间的关系解析公式, 进而获得了折射率理论计算公式. 利用该折射率公式对折射率提取值进行了非线性拟合, 发现提取值和理论值之间的误差很小, 这个结果很好地验证了所给出的本构矩阵解析式和折射率公式的正确性. 根据拟合结果, 获得了磁电耦合超材料本构矩阵中四个电磁参数的频率响应曲线. 所提出的磁电耦合超材料本构矩阵参数获取方法将为研究磁电超材料中电元件和磁元件的耦合现象提供重要的理论参考.     

周期性磁谐振材料本构参数的理论分析

将薄的磁谐振介质板等效为面磁流, 利用周期性边界条件, 给出了面磁流的指数形式. 通过计算无穷个面磁流在不同空间位置上产生的总电场和总磁场, 推导出了周期性磁谐振人工材料的色散关系和布洛赫阻抗, 进而获取了布洛赫本构参数的理论计算公式. 由于考虑了磁谐振人工材料中的电反谐振对布洛赫介电常数和磁导率的影响, 所以基于仿真实验的布洛赫本构参数的提取值和布洛赫本构参数理论预测值之间的误差很小, 这说明本文推导的布洛赫本构参数的理论计算公式在描述周期性磁谐振材料的电磁特性方面是十分有效的. 这些理论公式将在解释磁谐振现象、设计和优化周期性磁谐振材料等方面提供重要的理论依据. 关键词： 周期性结构 磁谐振 布洛赫本构参数 面磁流     

负折射率材料对Casimir效应的影响

研究了负折射率材料介质板间的Casimir效应.对于负折射率材料中由Drude-Lorentz型色散关系描述的介电常数和磁导率，色散曲线中负值频带的曲线结构由各色散吸收参数所决定，色散曲线负值频带宽度和负区域的深度等性质的变化影响了介质材料板的反射特性，进而对两材料板间的Casimir效应强弱起着重要的作用.     

对称磁电层合板磁电转换效应理论研究

磁致伸缩和压电层合材料通过磁致伸缩和压电效应的乘积可以获得大的磁电效应.通过材料的力学本构方程，建立了对称磁电层合板磁电耦合的静态力学模型；采用ANSYS 80多物理场有限元分析软件，对层合结构的磁电转化效应进行了数值计算，并与理论计算值进行了对比.研究结果表明：磁致伸缩/压电的厚度比增加使磁电电压系数增大；所推导的磁电电压系数公式的计算值与等效电路模型推导的公式计算值符合很好；有限元数值计算结果介于两种模型的计算结果之间. 关键词： 磁电效应 层合板 本构方程 有限元分析     

纵向极化与磁化叠层复合材料磁电效应理论及计算

基于纵向极化压电材料及纵向磁化磁致伸缩材料的压电和压磁方程与磁电元件运动方程,给出磁电元件开路电压表达式;鉴于压电材料高输出阻抗的特点,考虑测试仪器的有限输入阻抗和传输信号引线电缆电容,通过建立等效电路模型推出了非开路情况下磁电电压计算式,取不同材料参数对磁电电压进行了数值计算.研究表明,材料参数、电路参数对输出电压均产生影响.对磁伸材料两端面受非均匀偏置磁场产生外力的非自由边界磁电效应进行研究发现,恒外力作用使压电元件产生不可检测的稳恒电压. 关键词： 纵向极化 磁电效应 磁电元件 层叠材料     

有限输入阻抗下压电/磁伸层叠材料磁电效应理论及实验

将磁致伸缩材料及压电材料本构方程与运动方程结合,考虑压电材料具有的高输出阻抗的特点及测试设备的有限输入阻抗和传输信号引线电容对磁电效应输出电压的影响,推出了Terfenol-D巨磁伸材料与横向极化Pb(Zr_1-xTi_x)O₃压电材料的磁电效应理论,研制了由一维磁伸材料构成的三明治结构元件并对其性能进行了测试,采用考虑了测试系统有限输入阻抗后建立的磁电效应理论结果与实验结果更符合.理论结果表明磁电元件在有限输入阻抗 关键词： 磁电效应 有限输入阻抗 压电/磁伸复合 一维磁伸材料     

负折射率材料透镜的消色差

以工作在近红外波段0.848 μm～1.114μm,焦距100 mm,入瞳直径20 mm,具有负阿贝数的负折射率平凹透镜为例,介绍了两种对该类负折射率透镜的消色差设计方法,即利用正折射率材料透镜与负折射率材料透镜组合消色差和负折射率透镜中引入衍射光学元件实现折衍射混合透镜消色差方法.结果表明,正负折射率材料透镜组合消色差方法中正折射率材料透镜承担几乎全部光焦度,进而引入大量额外单色像差,但利用衍射光学元件可以在不引入额外像差的同时实现负折射率透镜的消色差.根据负折射率材料在介质与空气分界面的特殊折射特性,推导了以负折射率为基底的衍射光学元件的衍射效率公式,得到衍射微结构高度公式,求出不同波长处的衍射效率值.负折射率二元衍射光学元件在设计波长0.912 μm处衍射效率为40.53％,在波长0.848 μm处的衍射效率为35.06％,在波长1.114 μm处的衍射效率值为39.83％.     

周期性层状铁氧体-电介质复合材料中导模模式的有效负折射率

运用等效传输线法研究了周期性层状铁氧体-电介质/金属复合材料导模模式的有效折射率.通过对复合材料导模模式的色散特性和有效折射率的分析和计算，发现负折射率只能出现在TE模式激励下的某一频带内.在负折射率频带内的电磁损耗与复合材料中介电材料的性质密切相关，减小介电损耗可以有效降低复合材料的损耗，但过分小的介电损耗则会导致负折射率的消失. 关键词： 负折射率 导模模式 等效传输线法     

负折射率材料对产生Casimir排斥力的影响

研究了负折射率材料对产生Casimir排斥效应的影响. 两材料板间的Casimir排斥力的发生取决于两板以及其间媒质的电磁特性,通过理论与数值结果的分析研究给出电磁特性所影响排斥力的产生趋势. 对于由Drude-Lorentz型色散关系描述等效介电常数和磁导率的负折射率材料,调节各特征频率参数可实现Casimir排斥效应. 关键词： Casimir排斥力 负折射率材料 Drude-Lorentz型色散关系     

GMM/弹性板/PZT层状复合结构的纵振磁电响应

利用Hamilton原理推导GMM/弹性板/PZT三层层状复合结构的运动方程,在推导中考虑层间胶层的作用,包括其剪切变形和纵向变形产生的效果;应用运动方程,根据层状复合结构的边界条件,推导复合结构的固有频率方程,并结合压磁和压电方程,得到层状复合结构在不同固有频率处的磁电响应.对比磁电响应的频率特性的理论值和实验值,频率误差在9.42%以内,磁电电压转化系数的理论值与实验值符合,并讨论了弹性板的尺寸变化对层状复合结构谐振频率的影响. 关键词： 层状复合结构 磁电响应 Hamilton原理 运动方程     

含有异向介质H形波导的特性研究

将开口谐振环作为加载单元,分析了含有异向介质H形波导的新型传输特性.由于异向介质的双各向异性效应,纵剖面磁波型和纵剖面电波型在此新型导波结构中的相速度能够减慢,并且会引起功率流动的增强.在一些情况下,纵剖面磁波型和纵剖面电波型将出现传播常量随频率增高而减小的异常高次模式.而在其它情况下,利用双各向异性效应可以有效减少纵剖面磁和纵剖面电波型的高次模漏波现象.尤其当异向介质取得单负参量时,此新型导波结构将能够完全抑制高次模漏波的出现.     

Exploring electromagnetic response of tellurium dielectric resonator metamaterial at the infrared wavelengths

We numerically investigate the electromagnetic properties of tellurium dielectric resonator metamaterial at the infrared wavelengths. The transmission spectra, effective permittivity and permeability of the periodic tellurium metamaterial structure are investigated in detail. The linewidth of the structure in the direction of magnetic field W x has effects on the position and strength of the electric resonance and magnetic resonance modes. With appropriately optimizing the geometric dimensions of the designed structure, the proposed tellurium metamaterial structure can provide electric resonance mode and high order magnetic resonance mode in the same frequency band. This would be helpful to analyze and design low-loss negative refraction index metamaterials at the infrared wavelengths.     

Influence of the sign of the refractive index in the reflectivity of a metamaterial surface with localized roughness

To study the scattering properties of metamaterials, we generalize two scattering methods developed for conventional (non-magnetic) isotropic materials to the case of materials with arbitrary values (positive or negative) of magnetic permeability and electric permittivity. The generalized methods are used to study the changes produced in the reflectivity of a metamaterial surface with localized roughness when the relative refractive index changes sign. Our results show that, unlike the case of a plane surface whose reflectivity is unaffected by the change of sign of the relative refractive index, in rough surfaces the change of sign is manifested in the reflectivity, even for very low roughness, particularly in observation directions away from the specular direction.     

Research technique of metamaterials with the controlled effective negative refractive index and their characteristics

A design of the two-beam hybrid microwave interferometer for measuring refractive indices of metamaterials is described. It is based on the branching of radiation using a waveguide directional coupler. Radiations of the interferometer waveguide arms are summed and the phase disbalance of the interferometer arms is counted on the waveguide measuring line. The frequency dispersion of the negative refractive indices of the metamaterial samples with a variable distance between its constituent plates is experimentally investigated. A possibility of controlling the refractive index of a metamaterial is demonstrated.     

Material parameters of metamaterials (a Review)

A theory of the homogenization of a certain class of metamaterials is stated. These metamaterials are volume lattices of electric and magnetic dipoles that are resonant with frequencies that are considerably lower than that of the first Bragg resonance of the lattice. It was shown that, for plates of a metamaterial, which are described by bulk material parameters, transition layers play an important role, and the known Drude notion of transition layers is significantly revised. The paper also discusses a more widespread method of determining the material parameters of metamaterials based on the extraction of the refractive index and the characteristic impedance from the scattering matrix of the plate of the metamaterial. The physical meaning of the material parameters obtained in this way is clarified, and the concept of Bloch lattices related to it is discussed. It is shown that the bulk material parameters and the parameters of transition layers can also be extracted from components of the scattering matrix of plates.     

Investigation of negative index properties of planar metamaterials based on split-ring pairs

A low losses broadband planar negative refractive index metamaterial based on split-ring resonator (SRR) pairs is proposed and investigated experimentally and numerically at microwave frequency range. The transmission spectra of the single-layer SRR pairs were measured, and exhibited left-handed (LH) transmission passband clearly. The metal-dielectric-metal structure exhibits strong magnetic and electric responses simultaneously, and leads to negative permeability and negative permittivity. To further verify the LH properties of planer structure metamaterials, effect media parameters were retrieved, a refraction phenomenon based on a wedge-shaped model and negative phase advance between consecutive numbers of layers were also demonstrated.     

Copropagation of two pulses of different frequencies and modulation instabilities induced by cross-phase modulation in metamaterials

Nonlinear coupled equations describing the copropagation of two light pulses of different central frequencies in metamaterials (MMs) are derived. Based on the derived equations and the Drude model for dispersive MMs, the modulation instabilities (MIs) induced by cross-phase modulation (XPM) for different combination of the signs of refractive index experienced by the two optical pulses, respectively, are analyzed. It is shown that, in the absence of group-velocity mismatch, the property of MI only depends on the sign of group-velocity dispersion the two pulses experience, irrespective of the sign of refractive index. The group-velocity mismatch plays an important role in the occurrence of MI, especially when the central frequencies of the two pulses near the electric or magnetic plasma frequency of the MM. The theoretical results are confirmed by numerical simulations.     

Dynamical anisotropic magnetoelectric effects at ferroelectric/ferromagnetic insulator interfaces

The interfacial magnetoelectric interaction originating from multi-orbital hopping processes with ferroelectricassociated vector potential is theoretically investigated for complex-oxide composite structures.Large mismatch in the electrical permittivity of the ferroelectric and ferromagnetic materials gives rise to giant anisotropic magnetoelectric effects at their interface.Our study reveals a strong linear dynamic magnetoelectric coupling which genuinely results in electric control of magnetic susceptibility.The constitutive conditions for negative refractive index of multiferroic composites are determined by the analysis of light propagation.