【作者】 吕建红；

【导师】 胡希伟； 刘明海；

【作者基本信息】 华中科技大学 ， 脉冲功率与等离子体， 2010， 博士

【摘要】 电磁超材料作为一个新兴、多学科交叉领域,具备潜在的发展前景,因此近十年来受到广泛关注。本论文从研究电磁超材料对入射电磁波的电磁响应特性出发,构造设计了新型的单面左手材料、以及可以减小对电磁波极化方向依赖性的高维四重C-形状平面左手材料；研究了不同开口数单环谐振环之间的耦合效应以及由于耦合产生的磁分裂现象；另外,我们还基于光学变换理论、研究了电磁超材料在控制电磁波场分布中的应用(如波束偏转器、隐身斗篷)。本论文第一部分内容主要是研究新型电磁超材料的构造,及其在入射电磁波作用下的电磁响应特性。首先,我们详细分析了金属长细线(Rods)(或金属短线),与开口谐振环(SRRs)在不同相对排列情况下,电磁左手材料的负折射特性,经过模拟验证发现,当金属短线和谐振环共面、且彼此相连对称分布时,可以同时拥有宽通带、低损耗的优点。其次,我们设计了单面、结构简单、易于加工的双L形状的左手材料,并从理论和实验上对其负折射特性进行了验证,两种结果吻合,证实了设计的正确性；同时还详细分析了其负折射产生的机制,以及两种不同磁谐振模式的起因。然后,我们又设计了高维四重C-形状平面电磁左手材料,该设计减小了超材料对入射电磁波极化方向的依赖性,具有使不同方向入射、不同极化方式的电磁波均产生负折射率的特性；同时,对不同方向入射情况下,超材料的电磁响应特性及负折射产生的机制进行了详细分析和验证。最后,我们对同样极化方式下、不同开口数(1-开口、2-开口和4-开口)单环谐振环的电磁响应特性进行了详细研究,发现随着单环谐振环开口数量的增加,相邻谐振环之间的电磁耦合效应增强,4-开口时将会导致磁谐振模的分裂,形成两个不同起因的磁谐振模式；另外,通过调整4-开口谐振环的几何尺寸,我们构造了拥有超宽负磁禁带的单负电磁超材料。本论文第二部分主要是基于光学变换理论、研究了电磁超材料在控制电磁波场分布中的应用。首先,我们设计了基于有限嵌入坐标变换的多分支波束偏转器,使入射电磁波可以同时向不同方向、以不同角度无反射的偏转；同时还研究设计了两分支、交叉情况下的波束偏转器,虽然分支之间存在着耦合并使波形稍微变形,但依然可以使入射电磁波按预定角度无反射的偏转。其次,我们还研究了关于组合隐身斗篷、不规则隐身斗篷的边界阻抗的匹配性问题,通过合理设计隐身斗篷的电磁参数,大大降低了斗篷对入射电磁波的散射,并对其隐身效果进行了仿真验证。更多还原

【Abstract】 Electromagnetic metamaterial, a new and interdisciplinary field, has been received more and more attentions in the past ten years, for its potential development prospects. In this thesis, based on the electromagnetic response characteristics of the metamaterials, we construct new types single-sided structure left-handed metamaterials, and design a high dimensional four-fold C-shaped planar left-handed metamaterial, which can be reduce the effect of EM wave propagation direction on the metamaterial’s response; then we discuss the electromagnetic coupling between the single-ring SRRs (split-ring resonators) with different gaps (1-gap,2-gaps, and 4-gaps), and the splitting of the magnetic resonance caused by the electromagnetic coupling. Furthermore, based on the optical transformations, we discuss the applications of electromagnetic metamaterials in the controlling of electromagnetic wave, such as wave bender and invisible cloak.In the first part of this thesis, we investigate numerically the constructions of new types electromagnetic metamaterials, and their’s electromagnetic responses to the incident EM wave. Firstly, we detail analyze the negative refraction properties of different left-handed metamaterials (LHMs), of which the Rods (or cut wire) are printed in-plane, off-plane, and connected with respect to the symmetric paried split-ring resonator, respectively. With the simulation results, we conclude that the conncected case single-sided LHM can exhibit a simultaneous low-loss and broad left-handed pass-band, compared with the in-plane and off-plane cases.Secondly, we design a single-sided, easy fabricated left-handed metamaterial with double L-shaped resonator inclusions. In order to verify our design, both the numerical and experimental demonstrations are carried out, and the results agree well to each other. Then, the mechanism of negative refraction and the cause of two magnetic resonances of the double L-shaped resonator are detail explained and analyzed.Thirdly, we design and investigate a high dimensional four-fold C-shaped planar left-handed metamaterial, it can exhibits negative refraction with electromagnetic wave incidence in three different directions and with different polarizations. So it can reduces the effect of electromagnetic wave paopagation direction on the metamaterial’s response. Furthermore, the mechanism of the negative refraction and the electromagnetic responses of the four-fold C-shaped planar metamaterial to EM wave are discussed under the normal and parallel incidence case, respectively; and the left-handed property of this metamaterial is also demonstrated numerically.Lastly, we investigate the electromagnetic response of the single ring resonator with 1-gap,2-gaps, and 4-gaps, respectively. From the simulation results, we conclude that the electromagnetic coupling between the rings becoming stronger with the gaps increase; and the magnetic resonace mode will be splitted into two modes, due to the strong coupling between the neighbor rings for the 4-gaps case. Also, we construct a negative meganetic metamaterial with super-wide band-gap by asjusting the geometric parameters of the 4-gaps split-ring resonator.In the second part of this thesis, based on the optical transformations, we discuss numerically the application of electromagnetic metamaterials in controlling the EM wave. Firstly, we design a multi-branch wave bender by using finite embedded optical transformations, which can bents the electromagnetic wave simultaneously to different directions with different angles without reflection. Furthermore, we extend this wave bener, and design a crossed two branches wave bender, it can also bent the electromagnetic wave to the desired directions without reflection, though there exists coupling between two branches, and the wave shape is a little destroyed. Secondly, we investigate the impedance-matched problem between the boundaries of the combined cloaks, and the scattering of the electromagnetic cloak is substantially reduced after we have reasonably designed and modified the electromagnetic constitutive parameters of the cloak. Then, the full wave simulations are also carried out to demonstrate our designs and calculations.更多还原