【作者】 杨茜；

【导师】 伍瑞新；

【作者基本信息】 南京大学 ， 电磁场与微波技术， 2020， 硕士

【摘要】 随着通信技术的不断发展,天然材料已无法满足电磁传输中的多样化需求。因此,人工电磁材料(超材料)逐渐成为人们研究的热点。超材料作为一种新型材料,不仅能够操控材料的介电常数和磁导率,根据需求设计特定材料,更能够通过千变万化的微结构实现各种奇异的电磁现象,为各种电磁设备的设计提供了一种便捷的方法。和一般的天然材料相比,超材料的性能可人工调节的能力展现出了这种材料显著的优势。从结构种类的不同,超材料可以分为超表面、三维超材料以及具有一定厚度的准三维超材料。准三维超材料由于其维度和结构上的显著优势能够突破二维超材料的瓶颈,拓宽应用范围。且准三维超材料摒弃了三维超材料笨重、体积过大、结构复杂等缺点,有着更好的应用前景。3D打印是实现准三维超材料的一种低成本、高效率的方法,在多种3D打印技术中,以熔融层积成型技术FDM技术最具代表性,其工艺简单、耗材种类繁多、成本低廉,因此是应用最为广泛的3D打印技术。FDM技术可用于研究中,使实现准三维超材料更为便捷,研究周期缩短,同样也可应用在小型批量生产中。手性超材料在电磁波的传输调控中受到了极大的关注,可以用于实现旋光性、圆二色性、非对称传输等奇异的光学特性。而其往往具有复杂的三维手性结构,传统工艺实现较为困难。因此3D打印技术在手性超材料中的应用对电磁波的调控研究具有重要意义,本文基于3D打印技术,设计了多种手性准三维超材料,实现了圆二色性、非对称传输等光学特性,主要工作如下:一、本文设计两种结构互补的双层椭圆/椭圆槽结构,该两种结构采用层叠法引入手性特征。经过数值模拟证实椭圆槽结构的圆二色性优于双层椭圆结构,在15.5 GHz～18 GHz范围内表现出巨大的圆二色性,圆二色性参数峰值可达0.31。通过3D打印制作了双层椭圆槽结构7×7的样品并通过实验测量其传输特性及圆二色性参数,结果与仿真基本一致。二、本文通过堆叠法设计并比较了全介质及金属双L结构的非对称传输特性,其中金属结构效果更好,非对称传输系数峰值可达0.76。三、设计了两种具有三维单元结构的准三维超材料。第一种结构由分裂环旋转拉伸构成,能够实现接近1的非对称传输系数,且通过双开口后能够拓宽工作频带,在9.8GHz～14GHz实现宽带非对称传输。第二种结构具有双频带非对称传输特性,在10.8GHz非对称传输系数峰值可达0.96。利用3D打印技术及化学镀后处理工艺对这两种结构进行实验验证,但由于工艺问题实验结果与仿真有一定差距更多还原

【Abstract】 With the development of modern communication technology,natural materials cannot meet the diverse needs in electromagnetic control.Therefore,the study of artificial electromagnetic materials(metamaterials)has gradually become one of the research focuses.As a new type of material,metamaterials can not only control the permittivity and permeability of materials,and design specific materials on demands,but also realize various electromagnetic phenomenon through kaleidoscopic microstructures.And it provides a convenient method for the design of many electromagnetic equipment.Compared with ordinary natural materials,metamaterials’ properties can be adjusted manually and for this reason they show significant advantages.According to dimension,metamaterials can be classified into metasurfaces,three-dimensional metamaterials,and quasi-three-dimensional materials with a certain thickness.Quasi-three-dimensional metamaterials can break through the limit of twodimensional metamaterials due to its advantages in dimension and structure,and broaden the scope of application.Moreover,the quasi three-dimensional metamaterials overcome the shortcomings of the three-dimensional metamaterials,such as bulkiness,excessive volume,and complicated structure,and have better application prospects.3D printing is a low-cost and high-efficiency method for achieving quasi-threedimensional metamaterials.Fused deposition modelling(FDM)is the most representative method among many 3D printing technologies.It has a simple process,a wide variety of consumables,and is low cost.Therefore,it is the most widely used 3D printing technology.Using FDM technology,researchers can more easily explore and manufacture quasi-three-dimensional metamaterials,shorten the research cycle,and it can also be applied to small-scale batch production.Chiral metamaterials have received great attention in control of electromagnetic wave transmission,and can be used to achieve bizarre optical properties such as optical activity,circular dichroism,and asymmetric transmission.However,it often has a complex three-dimensional chiral structure,which is difficult to make with traditional processes.Therefore,the application of 3D printing in chiral metamaterials is of great significance to the study of electromagnetic control.In this article,we design several chiral quasi three-dimensional metamaterials to achieve optical properties based on 3D printing technology,such as circular dichroism and asymmetric transmission.The main work is as follows:1.Two complementary double-layer ellipse / elliptical slot structures are designed in this paper.The structures adopt the stacking method to introduce chirality.Through numerical simulation,it is confirmed that the circular dichroism of the elliptical slot structure is superior to the double-layer elliptical structure.A 7 × 7 sample with a double-layer elliptical slot structure was fabricated by 3D printing and its transmission and CD parameter was calculated through experiments.The results were basically consistent with the simulation.2.In this paper,we design and compare the asymmetric transmission characteristics of the all-dielectric and metal double-L structure.The metal structure has a better effect and the peak value of the asymmetric transmission coefficient can reach 0.76.3.Two quasi-three-dimensional metamaterials with three-dimensional unit structure are designed.The first structure is composed of twisted split ring,which can achieve an asymmetric transmission parameter close to 1.Its working band can be broadened by adding another rotating slit.and realize broadband asymmetric transmission from 9.8GHz to 14 GHz.The second structure has dual-band asymmetric transmission characteristics,and the peak value of the asymmetric transmission coefficient can reach 0.96 at 10.8GHz.The 3D printing technology and chemical plating were used to fabricate samples and verify the property of these two metamaterials.Experimental results and simulation results have similarity,but there is difference due the technological problems in fabrication.更多还原