双曲传输线特异材料的电磁特性研究

Hyperbolic metamaterials，being a particular class of artificial microstructure materials, are useful for engineering electromagnetic space and controlling electromagnetic transmission. Hyperbolic metamaterial is described by the diagonal permittivity tensor with the principal components being of the opposite signs which results in a hyperbolic shape of the isofrequency contours. Unusual properties which are difficult to be realized by natural materials are due to the hyperbolic isofrequency surfaces in the wave vector space. Investigation on electromagetic properties of hyperbolic metamaterial has become one of the most exciting areas in the photophysics and condensed physics fields, due to their unique physical properties and unmatched potential applications.. In this research program, based on transmission line approach we will study both theoretically and experimentally the electromagnetic peroperties of hyperbolic metamaterials at microwave frequencies. Firstly, we focus on the novel electromagnetic phenomenons induced by high wave vector transmitted waves in hyperbolic transmission-line metamaterials. This program mainly studies the Sub-wavelength propagation properties induced by the high transmitted wave and the anomalous refraction and reflection properties at the interfaces associated with hyperbolic metamaterial. Secondly, we will experimently investigate the novel electromagnetic properties of the near zero hyperbolic metamaterials. We will fabricate a prototype of two dimensional metamaterial using chip components mounted on a printed circuit board and describe a transition in the topology of the iso-frequency surface from a closed ellipsoid to an open hyperboloid by use of near zero hyperbolic transmission -line metamaterials. Lastly, on these basis, we will explore the possible applications of hyperbolic metamaterials in microwave communication. The results of the above-mentioned problems not only deepen the understanding of basic physical processes of electromagnetic wave propagation in hyperbolic metamterial, but also provides the scientific platform and ground for application research of hyperbolic metamaterials and the design of the novel electromagnetic devices.

双曲特异材料是一种用于操控电磁空间和电磁传输的特殊人工微结构材料。双曲线型等频面使其表现出自然界传统材料所无法具有的物理性质，因其独特的物理性质及无与伦比的潜在应用已成为相关领域新的研究热点。本项目拟基于传输线方法采用理论分析和实验研究结合的方式，研究双曲传输线特异材料的电磁特性。主要包括以下三个方面：双曲传输线特异材料中大波矢传输波诱导的新奇电磁现象，主要研究亚波长传输特性和特殊的界面透反射现象；近零双曲特异材料的奇异电磁特性，通过设计传输线参数实现介电系数近零的双曲特异材料并研究其电磁拓扑传输机制；在此基础上探索双曲特异材料在微波通讯中可能的应用。上述问题的研究成果，不仅会加深人们对双曲特异材料中电磁波传播基本物理过程的理解，而且可以为双曲特异材料的应用研究及新型电磁器件的研制提供科学基础。

特异材料是一种由特征尺寸远小于工作波长的结构单元所组成，具有自然界材料所不存在的电磁特性的人工材料。作为特异材料的一个重要分支，双曲特异材料由于其独特电磁波操控特性成为人们研究的焦点。双曲特异材料能通过多种方式操控电磁波，可以支持高k传输波；对电磁波的调控能够突破波长尺度等。双曲特异材料的另一个重要的研究方向是近零双曲色散关系的奇异电磁特性。我们针对基于高k传输波及近零双曲特异材料的新型光调控机制进行了深入研究。.首先，利用等效电路的方法分析了二维加载贴片电容电感的传输线的色散关系，实现了微波段双曲特异材料。并联贴片电感的加载增加了双曲色散关系的可调节性。我们通过引入锲形和方形二维复合左右手传输线实验研究了双曲特异材料的单方向传输性和亚波长聚焦特性。并且通过适当的选取结构参数设计出等频线非常平坦的近零双曲特异材料，我们发现不管入射角是多大出射射角都是垂直于界面。通过设计锲形的不同倾斜角度通过数值仿真和实验的方法研究了不同入射角下电磁波的传输特性。研究发现从正常材料以不同角度入射的电磁波的折射线是相同的。其次我们研究了双曲特异材料中放置一个点源，设置不同频率的点源，发现点源只是沿着一个很窄的宽度直线传输，验证了双曲特异材料的亚波长聚焦。最后将双曲特异材料的这种特性应用到Bessel光束的产生中，实现了具有传播方向上不发散，在传播过程中遇到障碍物后能够自愈的特性。. 上述研究成果将有利于探索双曲特异材料中光子调控的新机理和新手段，并揭示出双曲特异材料中重要的物理机制，对深入理解双曲特异材料中的物理现象提供了一个新的视角。利用特异材料实现了电磁波的单向传输、亚波长聚焦和Bessel光束，为新型电磁器件的研制提供科学基础。