基于石墨烯超材料可调谐调制器研究

发布时间：2018-10-13 11:34

【摘要】：近些年来,随着太赫兹波技术的逐渐成熟,太赫兹波在信息通信、高清成像、传感、安全及疾病检测等领域表现出极大的应用前景。然而,这些应用不仅需要可靠的太赫兹源及有效的探测器,还需要高性能的太赫兹功能器件,调制器就是众多功能器件中非常重要的一种。石墨烯凭借其突出的电场或磁场的调制性及在太赫兹波段特殊的光电特性,被用来设计调制太赫兹的光电器件。诸如吸波体、传感器、调制器等基于石墨烯的太赫兹器件得到研究与验证。室温下,石墨烯的高载流子迁移率为调制器调制速率的提高提供了坚实的依据,但单层石墨烯对太赫兹波的吸收非常有限,导致调制器的调制深度受到极大限制,这都对光源的稳定性及探测器的灵敏度提出了非常高的要求,同时这也降低了对于干扰的抵抗力。超材料作为一种人工材料利用金属表面载流子的集体振荡吸收太赫兹波,同时当石墨烯的介电常数虚部大于0时其表现为金属性,这为石墨烯与超材料结合用于提高太赫兹调制器调制速率提供了依据。本文结合石墨烯的电调谐与超材料的谐振吸收的特性,研究了基于石墨烯超材料深度可调的调制器、基于石墨烯超材料可调谐电磁诱导透明及基于入射光偏振方向的可调谐调制器。本文的主要研究内容及结论概括如下:1.研究了一种基于石墨烯超材料深度可调的调制器。建立了双层石墨烯互补型结构与电介质组成的模型结构,通过CST仿真研究得到了对应频率为11.85THz的一系列调制深度,其中最大调制深度可达96%以上。这一系列的调制深度可以通过电压调节石墨烯的费米能级来进行调制转换,将极大促进调制器在波整形中的应用,如生成正弦波、三角波及方波等。此外,运用谐振子模型对透射规律进行了分析。2.研究了基于石墨烯超材料可调谐诱导透明。通过数值模拟,得到石墨烯费米能级由1.2eV被调制到1.6eV时,透明窗口由1.7THz移至2.0THz,这表明该结构器件可用作可调谐太赫兹器件。另外,通过S参数反演得到等效群折射率,分析可知其等效群折射率较大且虚部值很小,表明可以作为慢光器件。最后,通过建立耦合谐振方程分析其原理机制。
[Abstract]:In recent years, with the development of terahertz wave technology, terahertz wave has shown great application prospects in the fields of information communication, high-definition imaging, sensing, security and disease detection. However, these applications require not only reliable terahertz sources and effective detectors, but also high performance terahertz devices. Modulators are one of the most important functional devices. Graphene is used to design terahertz devices because of its outstanding modulation of electric field or magnetic field and special photoelectric characteristics in terahertz band. Terahertz devices based on graphene, such as absorbers, sensors and modulators, have been studied and verified. At room temperature, the high carrier mobility of graphene provides a solid basis for the modulation rate of modulator. However, the absorption of terahertz wave by monolayer graphene is very limited, which greatly limits the modulation depth of modulator. The stability of the light source and the sensitivity of the detector are required, and the resistance to interference is also reduced. As an artificial material, metamaterials absorb terahertz waves by using collective oscillations of metal surface carriers, and exhibit gold properties when the imaginary part of the dielectric constant of graphene is greater than 0. This provides the basis for the combination of graphene and metamaterials to improve the modulation rate of terahertz modulator. Based on the characteristics of electrically tuned graphene and resonant absorption of metamaterials, a modulator based on the adjustable depth of graphene supermaterial is studied. Tunable modulator based on graphene supermaterial tunable electromagnetic induced transparency and polarization direction of incident light. The main contents and conclusions of this paper are summarized as follows: 1. A modulator based on the adjustable depth of graphene metamaterials is studied. A model of the complementary structure and dielectric structure of bilayer graphene is established. A series of modulation depths corresponding to 11.85THz frequency are obtained by CST simulation. The maximum modulation depth can reach more than 96%. This series of modulation depth can be modulated by adjusting the Fermi level of graphene, which will greatly promote the application of modulator in wave shaping, such as the generation of sine wave, triangle wave and square wave, etc. In addition, the transmission law is analyzed by using the harmonic oscillator model. 2. Tunable induced transparency based on graphene supermaterial was studied. By numerical simulation, when the graphene Fermi level is modulated from 1.2eV to 1.6eV, the transparent window is shifted from 1.7THz to 2.0THZ, which indicates that the structure can be used as tunable terahertz device. In addition, the equivalent group refractive index is obtained by S-parameter inversion. The analysis shows that the equivalent group refractive index is large and the virtual part is small, which indicates that it can be used as a slow light device. Finally, the principle and mechanism of the coupled resonance equation are analyzed.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN761

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