可电调谐超材料研究

超材料的谐振特性与其周期单元特性相关,周期单元的某一或是某几个参数的改变可以实现对超材料反射特性的调谐。利用有源集总元件的可变电阻特性,结合超材料设计,通过仿真优化和实验制备得到可电调谐超材料;分析对比了两种不同的布线方式所带来的不同的反射率特性和可调谐特性;并采用等效电路法对主动FSS层的阻抗特性进行了分析。     

On the dispersion of waves for the linear thermoelastic relaxed micromorphic model

Abstract

We present the complete set of constitutive relations and field equations for the linear thermoelastic relaxed micromorphic continuum and investigate its variants for wave propagation. It is found that the additional thermal effects give rise to new waves and generate couplings with longitudinal waves which are not existing in the relaxed micromorphic continuum without thermal effects. However, transverse waves go unaffected by the thermal properties. Thermal effects do not create any band gap in the dispersion curves of the model with three curvature parameters. The dispersion curves have been computed numerically for a particular model and compared with those presented in earlier studies.     

基于移位算子法高斯波束与双负介质板相互作用的FDTD分析

以磁导系数μ为例推导了处理双负介质本构关系的移位算子法.将μ表示以jω为自变量的Padé近似,用/t代替jω,过渡到时域,再引入离散时域移位算子代替时间微分算子来处理Padé近似形式的μ,进而推导出FDTD计算中时频电磁场中磁感应强度B和磁场强度H之间的关系.最后用基于移位算子的FDTD方法仿真了电磁波与各种双负介质板的相互作用:负折射、相位补偿、平凹双负透镜成像.     

Creation of Ghost Illusions Using Wave Dynamics in Metamaterials

The creation of wave‐dynamic illusion functionality is of great interest to various scientific communities because it can potentially transform an actual perception into the pre‐controlled perception, thus empowering unprecedented applications in the advanced‐material science, camouflage, cloaking, optical and/or microwave cognition, and defense security. By using the space transformation theory and engineering capability of metamaterials, a functional “ghost” illusion device, which is capable of creating multiple virtual ghost images of the original object's position under the illumination of electromagnetic waves, is proposed and realized. The scattering signature of the object is thus ghosted and perceived as multiple ghost targets with different geometries and compositions. The ghost‐illusion material, which is being inhomogeneous and anisotropic, is realized using thousands of varying unit cells working at non‐resonance. The experimental demonstration of the ghost illusion validates the theory of scattering metamorphosis and opens a novel avenue to the wave‐dynamic illusion, cognitive deception, manipulate strange light (or matter) behaviors, and design novel optical and microwave devices.     

十字架型超材料吸波特性及机理研究

设计了一种十字架型电磁超材料吸波体,采用CST studio suite 2009 频域求解器提取S 参数进行仿真研究,并计算了其吸波率,在24.65 THz 和35.25 THz 得到两个吸收峰,吸收率分别为0.83 和0.997。改变材料结构尺寸,在7.3 THz 达到完美吸收,吸收率接近于1。将THz 波段的超材料吸波体结构尺寸放大1000 倍,在GHz 波段同样可以达到完美吸收,说明超材料吸波体可通过对结构尺寸调节改变吸收波段。另外研究了这种吸波体的吸收机理,发现吸收主要在第一层的十字架金属单元层,可用于Bolometer 探测器的设计。     

A novel negative dielectric constant material based on phosphoric acid doped poly(benzimidazole)

Metamaterials or artificial negative index materials (NIMs) have generated great attention because of their unique electromagnetic properties. The main challenge in current NIM development is creating a homogenous NIM without the need of complex geometric architectures consisting of capacitors and inductors or aggregated fillers, but possessing a tunable plasma frequency. A natural material that can exhibit negative values for permittivity and permeability simultaneously has not been found, or discovered. If one can design a negative dielectric constant material with a tunable plasma frequency of interest, implementing negative permeability into the material or system would be much more readily achievable to create a metamaterial. In this regard, a novel negative dielectric constant material, which is an essential key to creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at frequencies of kHz to MHz because of its reduced plasma frequency and an induction effect. As temperature increased, the dielectric spectrum changed from a relaxation to a resonance behavior and exhibited a larger magnitude of negative dielectric constant at a lower frequency. The conductivity of the doped PBI measured as a function of both temperature and frequency followed the same trend as the dielectric constant. With respect to the dielectric constant and the conductivity data, it can be assumed that the origin of the negative dielectric constant is attributed to the resonance behavior of the highly mobile ions at elevated temperatures and high frequencies. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

太赫兹可控功能器件的研究进展

近年来太赫兹(THz)科学与技术的研究成为光学领域的研究热点,其在医学、通信和公共安全等领域具有深远的研究价值和重要的应用前景。但是THz波段功能器件尤其是可控功能器件匮乏,限制了太赫兹技术的进一步应用。表面等离激元光子学和奇异介质的出现有望改变这一局面,它能够在亚波长尺度对电磁波进行路由和操纵,有望成为下一代芯片技术的候选方案。首先介绍了基于表面等离体和奇异介质的可控太赫兹功能器件的物理机制,然后从电、磁、热、光四种主动控制手段来分别展示近年来太赫兹波段功能器件的研究进展,并从功能应用上对太赫兹功能器件进行了简单的分类总结,最后讨论了在应用中存在的问题和面临的挑战。     

含各向异性特异材料的一维光子晶体的传输特性

利用传输矩阵方法研究了含各向异性特异材料的一维光子晶体的电磁传输性质.结果表明,光子晶体具有全向的零平均折射率带隙.这种全向带隙几乎不受晶格尺度、波的极化方向和入射角的影响.当一缺陷引入到光子晶体中时,会有电磁缺陷模出现.零平均折射率带隙中的缺陷模与普通Bragg带隙中的缺陷模不同,几乎不受晶格尺度、波的极化方向和入射角的影响.这一性质将在全向反射镜或滤波器中具有潜在的应用价值.     

基于左右手传输线的定向耦合器

设计出了一种新型平衡混合左右手传输线结构,并利用该结构设计出了一种基于混合左右手传输线的平行耦合型微带定向耦合器。该结构类型的定向耦合器具有强耦合、宽带宽和高定向性等特点,为常规耦合器提供了一种替代。通过改变耦合线之间距离和组成耦合线的混合左右手传输线结构单元的数目,可以实现不同耦合度和带宽的定向耦合器,实现3dB～20dB范围内的任意耦合,具有较高的应用价值。