基于超材料和石墨烯的太赫兹主、被动调制器件研究

发布时间：2018-07-04 14:31

本文选题：太赫兹 + 调制器　；参考：《天津大学》2016年博士论文

【摘要】：太赫兹是近年来电磁波的研究热点,许多科研小组投入其中,与之相关的太赫兹源、太赫兹探测器等器件层出不穷。但是,太赫兹波段的调制器件却仍然比较匮乏,主要原因是很多自然界的材料在太赫兹波段没有响应。针对该研究背景,本论文利用人工超材料和石墨烯新型材料,结合理论、模拟仿真和实验三个方面,设计了太赫兹波的主、被动有效调制器件,具体内容包括:(1)太赫兹被动式可调带阻滤波器研究。应用基本的U形结构,通过改变两个U形结构的相对位置等参数,实现了调制范围为~0.3 THz的太赫兹带阻滤波器。用LMC等效电路模型预测出滤波器的共振频率,并且得到了电路模型中相应的电容、自感、互感的具体表达式和数值。(2)基于超材料和石墨烯的被动式太赫兹调制器研究。把非对称SRR结构与单层石墨烯结合,发现在太赫兹透过频谱幅值中,Fano谐振的变化比偶极子谐振的变化大。通过分析模拟得出的表面电流和电场分布,得到该现象是由Fano谐振处,电场被牢固地局域到电容缝隙处产生的。该现象也预示着Fano谐振可以用于传感石墨烯。(3)基于硅和石墨烯的主动式太赫兹调制器研究。把两层CVD石墨烯先后转移到N型硅基底上,同时外加连续绿光光泵和较低的外置偏压,实现了对太赫兹信号的类二极管调制:正向偏压时,太赫兹能通过;负向偏压时,太赫兹被截止。在光泵为420 mW,电压为-4 V条件下,得到最高调制深度为83%。利用CST软件、薄膜近似理论和Drude模型很好地重现了实验结果,并且得到了石墨烯的费米能级、介电常数等参数的具体数值。(4)基于超材料和石墨烯的主动式太赫兹调制器研究。把单层石墨烯转移到U形亚波长阵列上,在外加连续光泵和偏置电压下,石墨烯的电导率发生变化,进而LC谐振和太赫兹的透过随之改变。通过对比石墨烯和光电导硅层的电导率的不同,定性分析了石墨烯费米能级的变化。
[Abstract]:Terahertz (THz) is a hot research topic in recent years, and many research groups have been involved in it, and the related devices, such as terahertz sources, terahertz detectors and so on, are emerging in endlessly. However, terahertz modulation devices are still scarce, mainly because many natural materials do not respond in terahertz band. Aiming at this research background, the active and passive modulation devices of terahertz wave are designed by using artificial supermaterials and graphene new materials, combined with theory, simulation and experiment. The main contents are as follows: (1) the research of THz passive tunable band-stop filter. A terahertz bandstop filter with modulation range of 0.3 THz is realized by changing the relative position of the two U-shaped structures. The resonance frequency of the filter is predicted by using the LMC equivalent circuit model, and the corresponding expressions and values of capacitance, self-inductance and mutual inductance in the circuit model are obtained. (2) A passive terahertz modulator based on metamaterials and graphene is studied. By combining asymmetric SRR structure with graphene monolayer, it is found that the variation of Fano resonance in terahertz spectrum is larger than that of dipole resonance. By analyzing the surface current and electric field distribution obtained from the simulation, it is found that this phenomenon is produced by the Fano resonance and the electric field is firmly localized to the capacitance slot. This phenomenon also indicates that the Fano resonance can be used for sensing graphene. (3) the active terahertz modulator based on silicon and graphene is studied. By transferring two layers of CVD graphene to N-type silicon substrate successively, adding continuous green light pump and lower external bias voltage, the diode like modulation of terahertz signal is realized: at forward bias, terahertz can pass through, and at negative bias, Terahertz was closed. The maximum modulation depth is 83 when the pump is 420 MW and the voltage is -4 V. Using CST software, film approximation theory and Drude model, the experimental results are well reproduced, and the specific values of the Fermi level and dielectric constant of graphene are obtained. (4) the active terahertz modulator based on metamaterials and graphene is studied. When graphene monolayer is transferred to U-shaped sub-wavelength array, the conductivity of graphene changes under the condition of continuous pump and bias voltage, and the LC resonance and terahertz permeation change accordingly. The variation of Fermi level of graphene is qualitatively analyzed by comparing the conductivity of graphene with that of photoconductive silicon.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN713;TN761

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