基于超材料的太赫兹吸收体及光开关的理论研究

发布时间：2018-01-11 07:02

本文关键词：基于超材料的太赫兹吸收体及光开关的理论研究　出处：《中国科学院研究生院(西安光学精密机械研究所)》2015年硕士论文　论文类型：学位论文

【摘要】：超材料(Metamaterials)一般被定义为是一种由亚波长尺寸周期性结构单元构成,且具有天然媒质所不具有的反常物理特性的新型人工材料。基于这些独特的电磁性质,该类材料在诸多领域均有广阔的应用前景。尤其是对工作于太赫兹波段的超材料结构的研究工作,目前人们已经设计和制造出了各式各样的功能器件,包括有太赫兹滤波器、偏振器、调制器、吸收体和开关等。相比于传统器件,它具有易集成和重量轻等优点。本论文主要围绕基于超材料的太赫兹吸收体和光开关的理论研究及设计而展开,论文的主要工作内容如下:1.提出了一种垂直级联的超宽带太赫兹超材料吸收体。引入了一个由各金属层磁场谐振耦合而激发的额外吸收峰,用来增宽吸收谱。叠加之后的吸收谱对2.6-5.7 THz的正入射太赫兹波保持吸收率90%,而且吸收谱的半高全宽(FWHM)约是中心频率的95%。通过计算各共振频率的入射太赫兹波功率损耗,分析了额外吸收峰的产生机理。2.通过仿真研究了太赫兹波入射角和偏振角对吸收谱的影响。结果表明,当入射角不大于50o时,该吸收体仍能在2.5 THz左右的频率宽度内维持吸收率88%。同时,偏振角的改变对吸收谱幅值几乎不影响。因此该吸收体对入射太赫兹波的偏振不敏感。3.设计了一个基于非对称裂环共振器的太赫兹超材料开关。通过改变外加泵浦光强可实现开关在打开与闭合状态之间进行切换。从理论上具体研究了硅中载流子浓度与泵浦光强的关系,以及载流子的产生和衰减过程。4.为了分析光开关各共振的产生机理,计算了光开关在各共振频率处的电场分布和表面电流分布,结果发现有一些共振是由LC共振和高阶共振的共振耦合产生。进一步,利用两个简易模型等效光开关的打开和闭合状态,分析了光开关在工作过程中的模式切换效应。5.研究结果表明,在1.26-1.49 THz的开关窗口内,开关比大于10。改变介质层的介电常数和厚度,可对开关窗口的位置和宽度进行调节。调节范围约为0.3 THz。此外,该太赫兹光开关的响应时间可达到ps量级。
[Abstract]:Metamaterials) is generally defined as a subwavelength size periodic structural unit. New artificial materials with anomalous physical properties that natural media do not possess. Based on these unique electromagnetic properties. This kind of material has a wide application prospect in many fields, especially the research work on the structure of metamaterials working in terahertz band. At present, people have designed and manufactured various functional devices. Includes terahertz filters, polarizers, modulators, absorbers and switches. Compared with conventional devices. This thesis focuses on the theoretical research and design of terahertz absorbers and optical switches based on metamaterials. The main work of this paper is as follows: 1. A vertical cascade ultra-wideband terahertz supermaterial absorber is proposed, and an additional absorption peak excited by magnetic resonance coupling of metal layers is introduced. It is used to widen the absorption spectrum. The superimposed absorption spectra retain an absorptivity of 90% for the normal incident terahertz wave of 2.6-5.7 THz. Moreover, the absorption spectrum FWHM is about 95% of the central frequency. The power loss of the incident terahertz wave at each resonance frequency is calculated. The influence of incident angle and polarization angle of terahertz wave on absorption spectrum is studied by simulation. The results show that the incident angle is less than 50 o. The absorbent can maintain the absorptivity of 88g in the frequency width of about 2. 5 THz at the same time. Therefore, the absorber is insensitive to the polarization of incident terahertz wave. 3. A terahertz supermaterial switch based on asymmetric split ring resonator is designed. The switch switching between open and close states can be realized by adding pump light intensity. The relationship between carrier concentration and pump light intensity in silicon is studied in detail theoretically. In order to analyze the mechanism of optical switch resonance, the electric field distribution and surface current distribution of optical switch at each resonance frequency are calculated. It is found that some resonances are generated by the resonant coupling of LC resonance and high order resonance. Furthermore, two simple models are used to equivalent the open and closed states of optical switches. The mode switching effect of optical switch is analyzed. 5. The results show that the switch window is within 1.26-1.49 THz. The switching ratio is greater than 10. The position and width of the switch window can be adjusted by changing the dielectric constant and thickness of the dielectric layer. The adjustment range is about 0.3 THz. in addition. The response time of the terahertz optical switch can reach PS order.
【学位授予单位】：中国科学院研究生院(西安光学精密机械研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4;TB39

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