石墨烯超快太赫兹光学特性研究

发布时间：2018-06-18 20:00

本文选题：石墨烯 + 布洛赫方程　；参考：《中国矿业大学》2017年硕士论文

【摘要】：石墨烯独特的电子结构使其具有优良的超快光学特性,尤其是在太赫兹波范围内。因此本文对单层石墨烯的超快太赫兹非线性光学性质进行了研究。通过建立石墨烯的光学布洛赫方程,研究了连续的太赫兹光场下单层石墨烯的超快动态光学性质,并且引入了石墨烯的理论模型。采用理论解析的方法对布洛赫方程进行讨论,获得了石墨烯中载流子浓度,极化强度以及电流强度随时间变化的函数。研究结果表明,在太赫兹辐射光场下由于泡利不相容和能量守恒原理,使得石墨烯系统建立动态非平衡载流子并达到饱和的时间是20-200fs,载流子的浓度随着入射光频率的增大而增大,因此能够在1ps之内迅速产生光电流。石墨烯线性光学响应区是(?)evFE0thω;否则是石墨烯系统非线性光学响应区,E0和ω分别对应入射光的强度和频率,t为时间,vF是石墨烯狄拉克点附近电子的费米速度。同时研究发现光子能量hω越大,电极化强度以及光电流越强。我们的理论研究结果与已有的众多实验结果一致,这表明石墨烯在超快动态光学领域拥有重要的研究和应用价值。基于石墨烯的光学布洛赫方程理论,对单层石墨烯在太赫兹高斯脉冲光场下的光学特性也进行了研究。研究结果表明石墨烯在太赫兹波段具有非常显著的非线性超快光学特性,这是因为石墨烯是零带隙狄拉克系统,且在狄拉克点附近能量是线性分布的。同时研究发现石墨烯载流子浓度,极化强度以及电流强度随着太赫兹脉冲频率的增加而增加,这表明石墨烯在超快动态太赫兹领域拥有重要的研究和应用价值。
[Abstract]:Graphene has excellent ultrafast optical properties due to its unique electronic structure, especially in the terahertz wave range. Therefore, the ultrafast terahertz nonlinear optical properties of graphene monolayer are studied. By establishing the optical Bloch equation of graphene, the ultrafast dynamic optical properties of monolayer graphene under continuous terahertz light field are studied, and the theoretical model of graphene is introduced. The Bloch equation is discussed by theoretical analysis, and the functions of carrier concentration, polarization intensity and current intensity with time in graphene are obtained. The results show that under terahertz radiation field, because of Pauli incompatibility and energy conservation principle, It is found that the dynamic non-equilibrium carriers in graphene system can be set up and saturated for 20-200 fs. the carrier concentration increases with the increase of incident light frequency, so the photocurrent can be generated rapidly in 1ps. The linear optical response region of graphene is FE0th 蠅; otherwise, the nonlinear optical response region E0 and 蠅 of graphene system correspond to the intensity and frequency of incident light respectively. The time = v F is the Fermi velocity of electrons near the graphene Dirac point. It is also found that the greater the photon energy h 蠅, the stronger the polarization intensity and photocurrent. Our theoretical results are consistent with many experimental results, which indicates that graphene has important research and application value in ultrafast dynamic optics. Based on the theory of optical Bloch equation of graphene, the optical properties of graphene monolayer in terahertz Gao Si pulsed light field are also studied. The results show that graphene has very significant nonlinear ultrafast optical properties in terahertz because graphene is a zero-band gap Dirac system and the energy distribution is linear near Dirac point. At the same time, it is found that the carrier concentration, polarization intensity and current intensity of graphene increase with the increase of terahertz pulse frequency, which indicates that graphene has important research and application value in ultrafast dynamic terahertz field.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71

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