智能双曲超材料的设计与电场可调反常光学行为研究

发布时间：2018-04-23 16:03

本文选题：双曲超材料 + 智能流体　；参考：《西北工业大学》2015年硕士论文

【摘要】：超材料是一种由次波长结构单元构建的人工介质,它能表现出不同寻常的电磁、光、声等性质。双曲超材料是超材料中最为奇特的一种,它的介电常数或磁导率张量的一个主轴分量与其他两个主轴分量的值符号相反,导致它有拥有双曲型色散曲线,这种特性使双曲超材料拥有许多独特的性质。本文设计了新型的电场可调智能双曲超材料,并通过仿真研究了其电场可调反常光学行为,主要工作和结果概括如下:1.设计了一种电场可调智能流体基双曲超材料,这种超材料由二氧化硅包覆的金纳米棒与硅油组成。在外加电场下,Au@SiO2纳米棒会形成单轴取向晶格结构,由于Au在可见光区的负介电特性,会导致流体沿电场方向的介电常数为负,流体系统呈现等频双曲色散特点,因此,可以实现对于TM波的全角度光频负折射。我们计算了流体系统的有效介电常数张量与外加电场强度的关系,并用有限元仿真证实了电场诱导的光频负折射实现与可调变化行为,系统研究了纳棒直径/长度,芯壳配伍、颗粒浓度等对可调光频负折射实现和行为影响。另外,我们还证实了该智能流体基双曲超材料的聚焦行为,而当对流体系统施加一个非均匀电场时能够实现梯度负折射。2.设计了一种超薄的多层石墨烯基太赫兹吸收器,这种超材料吸收器是由单层石墨烯/MgF2多层堆垛结构单元排列在金膜平面上构成。我们在理论上证明了这种吸收器有着双带全吸收效果。由于有效介电常数的各向异性,石墨烯/MgF2多层堆垛结构单元有一个双曲色散。结构单元间的强电偶极子谐振和磁偶极子谐振使吸收器的阻抗和自由空间匹配,导致了在太赫兹范围内的两个完全吸收峰。这两个吸收峰对于入射电磁波偏振方向不敏感并随费米能级变化展现可调性,但吸收峰强度和频率取决于材料和多层结构的几何参数。被吸收的电磁波最终被转化为热量,因此这个吸收器展现了一个很好的纳秒加热效果。
[Abstract]:Metamaterials are artificial media constructed from subwavelength structure units, which can exhibit unusual electromagnetic, optical and acoustic properties. Hyperbolic metamaterials are the strangest of metamaterials. One of the principal axis components of its permittivity or permeability Zhang Liang is opposite to the value symbol of the other two principal axis components, which results in its having a hyperbolic dispersion curve. This property makes hyperbolic metamaterials have many unique properties. In this paper, a new type of electric field adjustable intelligent hyperbolic supermaterial is designed, and its electric field tunable anomalous optical behavior is studied by simulation. The main work and results are summarized as follows: 1. An intelligent fluid based hyperbolic supermaterial with adjustable electric field is designed, which consists of silica coated gold nanorods and silicon oil. Under the applied electric field, the Aur SiO2 nanorods form uniaxially oriented lattice structure. Due to the negative dielectric properties of au in the visible region, the dielectric constant of the fluid along the electric field is negative, and the fluid system presents the characteristics of iso-frequency hyperbolic dispersion. All angle optical negative refraction for TM wave can be realized. We calculate the relationship between the effective dielectric constant Zhang Liang of fluid system and the external electric field strength, and verify the realization of negative refraction of optical frequency induced by electric field and the adjustable variation behavior by finite element simulation. The diameter / length of nanorods and the compatibility of core and shell are systematically studied. The effect of particle concentration on the realization and behavior of negative refraction of tunable optical frequency. In addition, we also confirm the focusing behavior of the intelligent fluid based hyperbolic supermaterial, and the gradient negative refraction of the fluid system can be achieved when a non-uniform electric field is applied to the fluid system. An ultra-thin multilayer graphene THz absorber is designed. The supermaterial absorber is composed of single-layer graphene / MgF2 multilayer stacking structure units arranged on the gold film plane. We have theoretically proved that this absorber has double band full absorption effect. Because of the anisotropy of effective permittivity, the graphene / MgF2 multilayer stacking unit has a hyperbolic dispersion. The strong electric dipole resonance and magnetic dipole resonance between the structure elements make the impedance of the absorber match with the free space, resulting in two complete absorption peaks in the terahertz range. These two absorption peaks are insensitive to the polarization direction of the incident electromagnetic wave and can be adjusted with the Fermi energy level, but the intensity and frequency of the absorption peaks depend on the geometric parameters of the material and the multilayer structure. The absorbed electromagnetic wave is eventually converted into heat, so the absorber shows a good nanosecond heating effect.
【学位授予单位】：西北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB381

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