太赫兹波宽带超材料吸收器的结构设计与性能

发布时间：2018-11-21 19:56

【摘要】：超材料宽带吸收器,尤其是结构简单性能优良的宽带吸收器在电磁隐身,光电探测等方面都有极大的应用前景,是太赫兹超材料领域的研究热点。当前,许多太赫兹超材料宽带吸收器存在吸收带宽有限、制作复杂、占空比较低等问题,这在一定程度上限制了它的发展及应用。通常,超材料宽带吸收器的设计采用金属-介质多层交互叠加方式,或者周期内排列组合多个图形结构的方式。在太赫兹波段,这些设计方法对微加工水平或超材料尺寸提出了很高的要求,因此难以大幅度提高吸收带宽。本文通过对闭合金属环谐振特性和电磁波带宽叠加原理的研究表明,图案层的闭合金属环边长决定谐振峰的位置,不同金属环产生的谐振峰相对独立且相互影响较小,便于实现带宽叠加。基于此特性,本文中设计平面同心嵌套金属环结构使一系列窄带吸收峰在太赫兹波段相互叠加实现了宽带吸收。对其吸收特性的研究表明,该器件为偏振无关器件,吸收带宽为3.70THz,带宽中心频率比高达87.5%,对一定角度斜入射的TE、TM模式电磁波都能保持较高的吸收率,且吸收主要为金属的欧姆损耗,并成功的利用了阻抗匹配原理和干涉理论对宽带吸收进行分析。平面嵌套结构的超材料宽带吸收器不仅具有制作简单、占空比高等优点,而且改变金属线宽和金属环间距可以提高超材料的吸收率,改变闭合环数量可以控制吸收带宽。考虑到实际应用中热传导,热电信号提取等问题,基于同心嵌套金属环图形并结合天线结构的设计思想,采用螺旋金属线方式设计了吸收性能更为良好的太赫兹波宽带吸收器。该吸收器为偏振不敏感器件,吸收带宽高达5.26THz,在带宽内平均吸收率超过80%,带宽中心频率比接近90%。另外,利用天线结构对电场的放大作用和超材料设计的可缩放性,在微波波段结合集总元素和螺旋天线结构设计出了偏振无关的宽带吸收器。
[Abstract]:Ultra-material broadband absorbers, especially broadband absorbers with simple structure and excellent performance, have great application prospects in electromagnetic stealth, photoelectric detection and so on, and are the research hotspot in the field of terahertz supermaterials. At present, many terahertz supermaterial broadband absorbers have some problems, such as limited absorption bandwidth, complex fabrication, low duty cycle and so on, which limits its development and application to a certain extent. In general, the ultra-material broadband absorber is designed by metal-dielectric multilayer interaction superposition, or by permutation and combination of multiple graphic structures within a period. In the terahertz band, these design methods require high level of micromachining or the size of supermaterial, so it is difficult to increase the absorption bandwidth greatly. In this paper, the resonant characteristics of closed metal ring and the superposition principle of electromagnetic wave bandwidth are studied. It is shown that the side length of the closed metal ring determines the position of the resonant peak, and the resonance peak produced by different metal rings is relatively independent and has little influence on each other. Easy to achieve bandwidth stacking. Based on this characteristic, a planar concentric nested metal ring is designed to achieve wideband absorption by superposing a series of narrowband absorption peaks at terahertz band. The results show that the device is polarization-independent, the absorption bandwidth is 3.70 THZ, the ratio of bandwidth to center frequency is as high as 87.5, and the absorption rate of TE,TM mode electromagnetic wave with oblique incidence at a certain angle can be kept high. The absorption is mainly the ohmic loss of metal, and the impedance matching principle and interference theory are used to analyze the wideband absorption successfully. The supermaterial broadband absorber with planar nesting structure not only has the advantages of simple fabrication and high duty cycle, but also can improve the absorptivity of the supermaterial by changing the metal wire width and the metal ring spacing, and the absorption bandwidth can be controlled by changing the number of closed rings. Considering the problems of heat conduction and thermoelectric signal extraction in practical applications, a terahertz wave wideband absorber with better absorption performance is designed based on concentric nested metal ring pattern and antenna structure design idea. The absorber is a polarization-insensitive device with a absorption bandwidth of up to 5.26THz. the average absorption rate is over 80 in the bandwidth, and the bandwidth central frequency ratio is close to 90. In addition, a polarization-independent wideband absorber is designed by combining lumped elements and helical antenna structures in microwave band, taking advantage of the amplification effect of antenna structure on electric field and the scalability of metamaterial design.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4

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