左手材料结构的设计和特性设计

【作者】 路纲；

【导师】 弓巧侠；

【作者基本信息】 郑州大学 ， 光学， 2009， 硕士

【摘要】 左手材料(Left-handed metamaterials,LHM)是一种有效介电系数和磁导率同时为负的人工电磁材料,表现出一系列反常的电磁特性,如反常Doppler效应、反常Cherenkov辐射、反常Goos-H(a|¨)nchen位移、负折射效应和完美透镜效应等。LHM的发现被美国《科学》杂志评为2003年度十大科技突破之一,《今日材料》将其列入近50年中十大进展,是当前物理与电磁学研究领域中的前沿与热点。当前对左手材料的研究主要集中在新型左手材料结构设计和左手材料的实际应用。结构设计是实际应用的基础。从第一个在4.2GHz～4.6GHz具有负折射特性的金属谐振环线结构左手材料实验验证后,不断有新的结构被发现研究,其中有高介电系数电介质结构、半导体结构和表面等离子体渔网结构等,负折射的频带也从GHz扩展到THz和近红外,为实际应用打下基础。左手材料的是由单元结构周期排列组成。单元结构在电磁波的激励下,当单个单元结构远小于响应频率波长时,单个单元结构可以近似看作这个结构的原子,这个复合材料可以看成是均匀介质,具有有效的介电系数和磁导率,单个结构单元在响应频段下的电磁响应可以反应出整体结构的电磁特性。左手材料结构设计是本文的主要工作。在研究过程中,通过理论和数值模拟等方法建立起一套系统的研究方案:通过单个单元模型的建立,S参数提取,有限差分法对结构的电磁场分析,在全波下楔形模型数值模拟折射场,从理论到数值模拟研究左手材料的电磁特性。通过对金属劈裂环的电磁响应研究,设计了双层对置金属劈裂环结构,根据电磁场和谐振模式的分析,得出在两个频段该结构具有负有效介电系数和磁导率,全波下楔形模型数值模拟结果证实了这个结论。可调整响应频带的左手材料是研究方向之一。根据向列型液晶的特性,提出了金属劈裂环加液晶的三明治左手材料结构,将优化的金属环线结构单元与液晶相结合,通过外加电场调节液晶的介电系数,通过改变负的磁响应使该结构负折射响应中心频率可在一定范围内较方便、反复的调整,通过模拟仿真和理论分析证明这是一个可行的结构模型,具有一定的应用价值。更多还原

【Abstract】 Left-handed metamaterial (LHM) is a artificial electromagnetic material in which both the permittivity and permeability are simultaneously negative, perform extraordinary electromagnetic properties, such as reversed Doppler shift, reversed Cherenkov radiation, reversed Goos-Hanchen shift, negative refraction and perfect lens. The discovery of left-handed material has been regarded as one of the ten most significant discoveries in Science community in 2003. It was Materials Today’s top 10 advances in material science over the past 50 years and was the front and focus area in physics and electromagnetic research.Now the research of LHM is focus on the constructional design and application . The constructional design is fundament of all. When the first Split ring resonators(SRRs) which show negative refraction in 4.2GHz～4.6GHz was studied, some new constructional designs were found, such as high dielectric resonators, semi-conductor, and surface plasma fish-net etc, widen frequency band from GHz to THz and IR.Left-handed metamaterial is an arrangement of artificial structural elements designed to achieve advantageous and unusual properties. Under electromagnetic wave excitation, artificial structural element can be seen as atoms when the wavelength is much longer than the scale of single structural element, so single structural element can responded to electromagnetic properties of the artificial structural elements.In this paper, the constructional design was investigated. By the analytical and numerical studies ,a efficient and systemic schematic studies were proposed, included establish single structural element mode , Electromagnetic parameter retrieval from scattering (S) parameters, finite-difference-time-domain (FDTD) simulations , full wave wedge-shaped analysis simulations on realistic refraction index .A novel opposite Split ring resonators was presented by analysis of electromagnetic field and mode of resonance, it is investigated to show their negative refraction at the two frequency bands ,and the result is verified by full wave wedge-shaped analysis simulations.The controllable Left-handed metamaterials structure is another focus of my research. A planar metamaterials structure using liquid crystals sandwiched between layers of split ring resonators was demonstrated. This optimized structure has tunable negative index of refractive on account of a controlled permittivity of the liquid crystals drived by extend field. The frequency range with negative index of refractive can be adjusted conveniently and reversibly. Numerical simulation and analyzation show this is a valid and valuable Left-handed metamaterials structure.更多还原