發(fā)布時間：2018-10-13 11:34

【摘要】：近些年來,隨著太赫茲波技術(shù)的逐漸成熟,太赫茲波在信息通信、高清成像、傳感、安全及疾病檢測等領(lǐng)域表現(xiàn)出極大的應(yīng)用前景。然而,這些應(yīng)用不僅需要可靠的太赫茲源及有效的探測器,還需要高性能的太赫茲功能器件,調(diào)制器就是眾多功能器件中非常重要的一種。石墨烯憑借其突出的電場或磁場的調(diào)制性及在太赫茲波段特殊的光電特性,被用來設(shè)計(jì)調(diào)制太赫茲的光電器件。諸如吸波體、傳感器、調(diào)制器等基于石墨烯的太赫茲器件得到研究與驗(yàn)證。室溫下,石墨烯的高載流子遷移率為調(diào)制器調(diào)制速率的提高提供了堅(jiān)實(shí)的依據(jù),但單層石墨烯對太赫茲波的吸收非常有限,導(dǎo)致調(diào)制器的調(diào)制深度受到極大限制,這都對光源的穩(wěn)定性及探測器的靈敏度提出了非常高的要求,同時這也降低了對于干擾的抵抗力。超材料作為一種人工材料利用金屬表面載流子的集體振蕩吸收太赫茲波,同時當(dāng)石墨烯的介電常數(shù)虛部大于0時其表現(xiàn)為金屬性,這為石墨烯與超材料結(jié)合用于提高太赫茲調(diào)制器調(diào)制速率提供了依據(jù)。本文結(jié)合石墨烯的電調(diào)諧與超材料的諧振吸收的特性,研究了基于石墨烯超材料深度可調(diào)的調(diào)制器、基于石墨烯超材料可調(diào)諧電磁誘導(dǎo)透明及基于入射光偏振方向的可調(diào)諧調(diào)制器。本文的主要研究內(nèi)容及結(jié)論概括如下:1.研究了一種基于石墨烯超材料深度可調(diào)的調(diào)制器。建立了雙層石墨烯互補(bǔ)型結(jié)構(gòu)與電介質(zhì)組成的模型結(jié)構(gòu),通過CST仿真研究得到了對應(yīng)頻率為11.85THz的一系列調(diào)制深度,其中最大調(diào)制深度可達(dá)96%以上。這一系列的調(diào)制深度可以通過電壓調(diào)節(jié)石墨烯的費(fèi)米能級來進(jìn)行調(diào)制轉(zhuǎn)換,將極大促進(jìn)調(diào)制器在波整形中的應(yīng)用,如生成正弦波、三角波及方波等。此外,運(yùn)用諧振子模型對透射規(guī)律進(jìn)行了分析。2.研究了基于石墨烯超材料可調(diào)諧誘導(dǎo)透明。通過數(shù)值模擬,得到石墨烯費(fèi)米能級由1.2eV被調(diào)制到1.6eV時,透明窗口由1.7THz移至2.0THz,這表明該結(jié)構(gòu)器件可用作可調(diào)諧太赫茲器件。另外,通過S參數(shù)反演得到等效群折射率,分析可知其等效群折射率較大且虛部值很小,表明可以作為慢光器件。最后,通過建立耦合諧振方程分析其原理機(jī)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.
【學(xué)位授予單位】：山東科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN761

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