基于太赫兹石墨烯超常媒质的可调谐电磁诱导透明研究

发布时间：2018-03-28 16:06

本文选题：太赫兹　切入点：石墨烯　出处：《哈尔滨理工大学》2017年硕士论文

【摘要】：太赫兹(THz)超常媒质电磁诱导透明(EIT)是一种在THz波段用人造周期性结构单元形成的电磁现象,其在THz传输的频域谱上具有一个典型的透明窗口,对于慢光、光存储以及光传感的实现具有很重要的意义。然而,周期性结构单元形状和尺寸的固定使得EIT的透明窗口相对固定,无法进行动态调制,大大制约了器件功能的实现。本文针对目前国内外的一些可调谐EIT实现方式不易、调制深度不足的特点,利用石墨烯在不同外加偏压下具有变化较大的电导率的属性,提出了两种基于石墨烯的可调谐EIT超常媒质结构,主要研究工作如下:1、提出一种金-石墨烯交叉型EIT超常媒质结构,该结构由内部的金开口环结构和外部的闭合石墨烯环结构相互嵌套而成。为了分析EIT的形成机理,采用数值仿真软件分别对单独的金结构和石墨烯结构进行谐振特性研究,对形成的EIT谐振谷和透明峰处的表面电流进行监测,仿真结果表明该结构具有明-暗模式耦合的特点。通过改变石墨烯的费米能级,金-石墨烯结构呈现出不同的EIT响应特点,并对EIT的可调谐特性进行分析,计算透明窗口处的调制深度以及相应的群延迟,计算结果表明,该结构能实现幅值调制和慢光调制。2、为了获得EIT固定频率处透明峰的动态调制以及更大的调制深度,提出一种石墨烯-石墨烯超常媒质结构,该结构由左侧的石墨烯短线条和右侧的双闭合石墨烯环组合而成。采用数值仿真软件优化左右石墨烯间的相对距离,在此基础上,分析EIT的形成机理并证明了该结构明-明模式耦合的特点。通过同时改变左右两侧石墨烯结构的费米能级,石墨烯-石墨烯结构呈现出不同的EIT响应特点,并对EIT传输与吸收的可调谐特性进行分析,计算透明窗口处的调制深度以及群延迟的大小。计算结果表明,该结构能实现在固定频率处透明峰的幅值调制和慢光调制,并具有更大的调制深度。3、提出一种二粒子耦合模型并与仿真得到的EIT曲线进行拟合,拟合曲线与数值仿真曲线匹配度良好。拟合结果表明二粒子耦合模型及耦合模式理论分析的准确性。
[Abstract]:The electromagnetic induced transparency of terahertz (THZ) medium is a kind of electromagnetic phenomenon formed by artificial periodic structure unit in THz band. It has a typical transparent window in the frequency domain spectrum of THz transmission, for slow light. The realization of optical storage and optical sensing is of great significance. However, due to the shape and size of the periodic structure unit, the transparent window of EIT is relatively fixed and can not be dynamically modulated. The realization of the device function is greatly restricted. In this paper, some tunable EIT methods at home and abroad are not easy to be realized and the modulation depth is insufficient. In this paper, the graphene has the properties of varying conductivity under different applied bias voltage. Two kinds of tunable EIT supernormal medium structures based on graphene are proposed. The main research work is as follows: 1. A gold-graphene cross-type EIT supernormal medium structure is proposed. In order to analyze the formation mechanism of EIT, the resonant characteristics of individual gold structure and graphene structure are studied by numerical simulation software. The surface current of the formed EIT resonance valley and transparent peak is monitored. The simulation results show that the structure has the characteristics of light-dark mode coupling. By changing the Fermi level of graphene, the gold-graphene structure presents different characteristics of EIT response. The tunable characteristics of EIT are analyzed, the modulation depth at transparent window and the corresponding group delay are calculated. The results show that, This structure can realize amplitude modulation and slow light modulation. In order to obtain the dynamic modulation of transparent peak at fixed frequency of EIT and to increase the modulation depth, a novel graphene graphene supernormal medium structure is proposed. The structure consists of short graphene lines on the left and double closed graphene rings on the right. The relative distance between the left and right graphene is optimized by numerical simulation software. The formation mechanism of EIT is analyzed and the characteristics of the coupling between the open and open modes are proved. By simultaneously changing the Fermi level of the graphene structure on the left and right sides, the graphene graphene structure presents different EIT response characteristics. The tunable characteristics of EIT transmission and absorption are analyzed and the modulation depth and group delay at the transparent window are calculated. The results show that the structure can realize the amplitude modulation and slow light modulation of the transparent peak at fixed frequency. A two-particle coupling model is proposed and fitted with the simulated EIT curve. The fitting results show that the two-particle coupling model and the theoretical analysis of the coupling mode are accurate.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;O441.4

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