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     

各向异性超常媒质矩形波导的导波特性研究

研究中通过建立和求解填充各向异性超常媒质的矩形波导TE模式和TM模式的波动方程和场分布方程,讨论了各向异性超常媒质矩形波导的有效介电常数、有效磁导率、相位常数以及传输系数与所填充超常媒质本构参数之间的变化关系.研究发现,填充了各向异性超常媒质的矩形波导的导波特性在截止频率之上的频率区域,其导波特性由所填充超常媒质的横向本构参数决定,而与超常媒质的纵向本构参数无关.但是,在截止频率之下的频率区域,该矩形波导的导波特性则由所填充超常媒质的横向本构参数和纵向本构参数共同决定.研究中通过典型的计算实例对所得到的结 关键词： 各向异性 超常媒质 矩形波导 导波特性     

Transmission characteristics of wave modes in a rectangular waveguide filled with anisotropic metamaterial

In this paper, transmission characteristics of wave modes in a rectangular waveguide filled with lossless anisotropic metamaterial are theoretically investigated. The wave equation and dispersion relations for TE and TM modes in the waveguide are obtained and analyzed. It is shown that the negative constitutive parameters of the filling anisotropic metamaterial can be used to control the wave magnitude and the phase velocity direction in the waveguide over the entire frequency domain, both below and above the cutoff frequency. Particularly, not only backward waves, but also forward waves can propagate below the cutoff frequency in the waveguide. Furthermore, a typical example is calculated to demonstrate transmission characteristics of waves inside the waveguide. Numerical results are obtained in the paper and compared with theoretical predictions: a good agreement is found.     

基于TE10矩形波导的异向介质有效本构参数提取算法

提出了一种基于TE₁₀矩形波导的异向介质有效本构参数提取算法,利用该算法提取了对称多元胞铁氧体和金属线阵复合型异向介质的有效介电常数ε和有效磁导率μ.文中着重探讨了多元胞异向介质传播常数β实部的分枝选取问题,借鉴了测量理论中测量值和理论真值之间的关系,将单元胞的β提取值作为多元胞β的测量值,进而确定多元胞β的真实值;由于在多元胞异向介质各元胞之间存在耦合效应,使电磁波主要以周期性Bloch波的形式存在 关键词： 10矩形波导')" href="#">TE₁₀矩形波导 异向介质 有效本构参数提取 铁氧体和金属线阵异向介质     

A retrieval method for nonlinear metamaterials

Metamaterials are engineered periodic structures for which it is possible to assign effective homogenized constitutive properties. In recent years, metamaterials in which the constituent elements are integrated with inherently nonlinear materials or electronic components have been considered for their potential impact on nonlinear wave propagation. As is the case with their linear counterparts, nonlinear metamaterials can also be assigned homogenized effective properties. The effective constitutive parameters of a metamaterial can be determined by a retrieval method applied to full-wave numerical simulations of a single layer of the structure. In this work, we present a transfer matrix approach that extends the retrieval of metamaterial properties to include the effective nonlinear susceptibilities. Comparisons with time-domain finite element simulations of continuous nonlinear slabs confirm the validity of this approach. The proposed approach is also applied to determine the nonlinear susceptibility of a simple nonlinear metamaterial.     

Normal Waves in an Electromagnetic Metachiral Isotropic Medium with Losses

Russian Physics Journal - Electromagnetic plane waves in an isotropic absorbing chiral medium (chiral metamaterial) are considered. The Drude–Born–Fёdorov system of constitutive...     

Designing polarization insensitive negative index metamaterial for operation in near infrared

Hexagonal arrays of gold nanoelements with C₃ symmetry are studied as a metamaterial slab of reduced anisotropy. Tri-dimensional (3D) finite-difference time domain (FDTD) simulations are used to calculate the reflected and transmitted electromagnetic field for two waves normally incident to the slab with mutually perpendicular polarizations. S-parameter method is used to retrieve the constitutive parameters for each polarization. While dipolar plasmonic resonance in the case of one layer metamaterial slab leads only to negative values of permittivity, using two layers of asymmetric nanoelements leads to a negative refractive index metamaterial in the near infrared range (158–172 THz) as a result of hybridized plasmonic states inversion.     

Conversion from constitutive parameters to dispersive transmission line parameters for multi-band metamaterials

Abstract

In this study, we explain an approach including conversion from constitutive parameters to dispersive transmission line parameters using the double-band DNG (double-negative) properties of the circular type fishnet metamaterials. After designing the metamaterial structure, the numerical calculations and the composite right/left-handed (CRLH) modeling of circular-type metamaterials are realized in free space. Detailed dispersion characteristics give us the opportunity to explain the true behavior of the inclusions during the analysis stage. By combining the results coming from the standard retrieval procedure with the conventional CRLH theory, we calculate the actual values of the transmission line parameters for all frequency regimes. The constitutive parameters of an equivalent CRLH transmission line are derived and shown to be negative values. It is shown that the constitutive parameters present the same behavior for all negative refractive index regimes. The double-negative properties and the phase advance/lag behavior of metamaterials are observed based on the dispersive transmission line parameters.     

Retrieval of the effective constitutive parameters from metamaterial absorbers

The equivalent medium theory of metamaterials provides a way to obtain their effective constitutive parameters. However, because of its non-reciprocity, the complexity of the electromagnetic coupling, and a metallic bottom layer, it has been challenging to retrieve them from a metamaterial absorber. In this paper, we propose a method without any approximation to obtain them, in which the non-reciprocity and the strong electromagnetic coupling are included. Compared with the three methods such as symmetric metamaterial method, asymmetric metamaterial method and metasurface method, our method can reveal the metamaterial absorber's electrical and magnetic resonance and show its electromagnetic coupling coefficients. To deal with a metamaterial absorber with a metallic bottom layer, four corners of the metallic bottom layer in the unit cell are removed, making it possible to retrieve the electromagnetic parameters. Surprisingly, these results show that the metamaterial absorber with a metallic bottom layer in our example operates in a negative refraction state at the half absorption frequencies, which helps further understand the absorbing mechanism of these metamaterial absorbers.     

Properties of near and far fields for the electric line source illumination of a lossless metamaterial covered conductor cylinder

This work concentrated on an ELS (electric line source) radiating parallel to a lossless metamaterial covered infinitely long conductor cylinder. First, the exact analytical solution of the electromagnetic model is derived. Second, the numerical results based on the solution are given. Under different geometric and electromagnetic parameters, the patterns of the near field are obtained; the directivity and normalized radiation resistance are presented to discuss the properties of the far field. Because of the negative refraction of the metamaterial, it can be seen that there is a distinct “focus” in the metamaterial layer from the near field pattern, which does not exist in conventional material layer. The presented electromagnetic model is compared with the former, simpler model through the directivity and its validity is proven. PACS 78.70.Gq; 81.05.Zx; 84.40.Ba     

Study of a microstrip antenna on anisotropic metamaterials

The annular ring microstrip antennas on metamaterial substrates are modeled and analyzed using full-wave analysis in conjunction with Ansoft HFSS^TM. The influence of the permeability tensor of the split ring resonator medium on the resonant characteristics of the antenna is considered. Numerical results for typical resonant frequency behavior and return loss are presented as function of the metamaterial properties and antenna structural parameters.     

Permeability retrieval in InP-based waveguide optical device combined with metamaterial

An InP-based Mach-Zehnder interferometer combined with a metamaterial layer consisting of a split-ring resonator array was constructed to measure the complex permeability of the metamaterial. At a wavelength of 1.5 μm, the metamaterial showed non-unity relative permeability induced by magnetic interaction with propagating light in the device. This method of measurement would be useful to determine constitutive parameters in such waveguide-based photonic devices, allowing us to design photonic integrated circuits that make use of metamaterials.     

Infrared response of a metamaterial made of gold wires and split ring resonators deposited on silicon

Periodic arrays of gold wires and split ring resonators (SRR) with a minimum feature size of 50 nm are fabricated on low-doped silicon. To our knowledge, the periodic arrangement of SRRs and wires considered in this work has not been studied in the near-infrared domain yet. For normal-incidence conditions, this metamaterial structure exhibits resonances at 70 and 170 THz (i.e., at λ ≈ 4.3 and 1.75 μm), which are identified as LC- and Mie resonances, respectively. These resonances are also observed for the SRRs alone, but the amplitude of the Mie resonance is reinforced due to the coupling between the SRRs and wires. The structure is simulated using finite-element software, while transmission and reflection measurements are performed with a Fourier transform infrared spectrometer. Numerical simulations are found to be in very good agreement with experimental characterizations, thereby showing that the Drude model used in calculations is well suited to simulate gold structures at near-infrared frequencies. Theoretical calculations predict that the metamaterial has a negative permittivity and a negative permeability near each resonance.     

Enhancement of cross-polarized beam components at a metamaterial surface

Beam-interface interactions under incidence of a TE polarized elegant Hermite–Gaussian beam are considered in order to obtain efficient excitation of higher-order beam modes at a homogeneous, isotropic metamaterial surface. It is shown by numerical simulations that two transmitted TE and TM polarization beam components are enhanced more efficiently at a metamaterial surface than in the case of a dielectric interface. The mixed Poynting vector contribution to the incident energy flux is evaluated to explain this enhancement. The numerical results obtained are verified against energy balance at the interface.     

Extreme acoustic metamaterial by coiling up space

We show that by coiling up space using curled perforations, a two-dimensional acoustic metamaterial can be constructed to give a frequency dispersive spectrum of extreme constitutive parameters, including double negativity, a density near zero, and a large refractive index. Such an approach has band foldings at the effective medium regime without using local resonating subwavelength structures, while the principle can be easily generalized to three dimensions. Negative refraction with a double negative prism and tunneling with a density-near-zero metamaterial are numerically demonstrated.     

交指电容加载的周期性对称负磁导率人工材料研究

利用二端口网络理论和弗洛奎定理, 详细分析了周期性对称磁谐振人工材料的相对布洛赫磁导率与散射矩阵参数的关系, 利用这个关系提取了四种形式的开口谐振环布洛赫磁导率. 全波仿真和磁导率数值提取结果表明, 在开口谐振环的开口处加载交指电容, 磁谐振频率将显著降低. 这些成果将为提取周期性人工材料的布洛赫磁导率提供理论依据, 同时为小型化磁谐振特异人工材料提供新的设计思路.     

Reconfigurable subwavelength waveguide based on magnetic metamaterial

The design and characterization is described of a reconfigurable subwavelength waveguide based on magnetic metamaterial. The waveguide is capable of reconfiguring its propagating mode from right-handed to left-handed, which can be applied in the design of novel microwave and RF devices such as leaky wave antennas with broadened scanning range. The waveguide consists of a rectangular metallic waveguide loaded by two pieces of different magnetic metamaterials, which are structured by the same cells—modified split ring resonators (MSRRs)—with different arrangements. Positions of the two pieces of metamaterials in the waveguide can be reconfigured separately by the control mechanism. The simulated transmission data show that the waveguide has a passband below the cutoff frequency of the hollow waveguide either in the left-handed case or in the right-handed case. The extracted constitutive parameters have demonstrated that the effective permittivity and permeability of the waveguide are simultaneously negative in the left-handed case and positive in the right-handed case. The magnetic field and surface current distributions in the waveguide confirm that the waveguide operates as can be expected. The influence of the control mechanism on the performance of the waveguide is studied. It is shown that the influence is so minor that it can be neglected.     

Tunable dual-band ferrite-based metamaterials with dual negative refractions

We report on three types of tunable dual-band metamaterial with dual negative refraction in this paper. The three types of metamaterial are composed of ferrite slabs and three different metallic resonators, including split-ring resonators (SRR), Ω-like resonators, and short wire pairs. The ferrite slabs under an applied magnetic bias provide one magnetic resonance frequency band and the three metallic resonators provide another magnetic resonance frequency band, respectively. The continuous wires within the metamaterials provide the negative permittivity in a wide frequency band covering the two magnetic resonance bands. We give the design, analysis and numerical demonstrations of three such types of metamaterial in detail. The effective electromagnetic parameters obtained from the simulated S-parameters indicate that the three types of metamaterial indeed exhibit two negative refraction passbands and the two passbands can also be shifted by changing the magnetic bias. Our results open the way to fabricate tunable dual-band metamaterial cloaks, absorbers, and antennas.     

Characterization and electromagnetic response of a ?-shaped metamaterial

In this paper we experimentally and numerically study the left-handed behavior in a biplanar metamaterial operating at microwave frequency. The metamaterial consists of ϕ-shaped metallic patterns on both sides of a dielectric spacer. The origin of negative refractive index is elucidated by performing the effective medium analysis. Additionally, the dependence of the left-handed transmission on geometric parameters, such as the periodicities, the shapes of metallic slabs and continuous wires, and the impact of spacer separation, is examined.