低维金属和石墨烯结构表面等离激元近场性质的研究

发布时间：2018-03-15 22:18

本文选题：表面等离激元　切入点：银纳米线　出处：《中国科学院大学(中国科学院物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：表面等离激元是束缚在材料-介质表面的电荷密度波和表面电磁波相互耦合而引起的元激发模式。表面等离激元突破衍射极限传播和局域电场增强的特性,使其受到了广泛的关注和研究。特定波长的激光,可以激发特定材料,如金属或石墨烯等中的表面等离激元。其中,金属纳米线结构,作为表面等离激元的良好载体,可以支持不同表面等离激元模式。而二维石墨烯材料,具有表面等离激元的可调节性质和更小的传输损耗,可更好的用于光电子信息传输和探测。本论文将通过实验和模拟相结合的方法,对一维金属纳米线结构和一维石墨烯褶皱缺陷的表面等离激元近场性质进行研究。一维金属纳米线结构,同时支持传播型和局域型的表面等离激元。我们在实验上,利用溶液中微小颗粒的运动证实了金属纳米线表面等离激元近场光学力的存在。通过对纳米颗粒运动状态的分析,我们发现其沿线方向的运动,主要由等离激元传输损耗造成的热效应驱动。基于此,我们利用不同结构银纳米线以及激光激发偏振的改变,实现了对纳米颗粒运动的远距离定向调控。而石墨烯表面存在的一维褶皱缺陷,虽然结构尺寸微小,却会影响表面等离激元的传播。我们利用扫描近场光学显微技术,实现了对石墨烯褶皱的近场光学成像。通过对其实空间成像的分析及数值拟合,我们发现褶皱形貌造成的反射效应非常小,而导致其反射表面等离激元波的主要原因是褶皱处光电导的变化。并且,通过褶皱特性的改变,我们可以调控其对表面等离激元波的反射效应。另外,石墨烯条带的边界和褶皱均会对表面等离激元波造成反射。我们通过扫描近场成像技术,得到了两种叠加效应下的实空间成像。将实验结果结合理论分析发现,对不同类型光电导变化的褶皱,两者叠加的效果完全相反。光电导的增加,会造成其综合效果大于单纯边界,即相干相长;而光电导的减小,会造成其综合效果小于单纯边界,即相干相消。也就是说,我们可以通过近场光学成像的方法分析和判断褶皱处的光学和电学性质。总之,低维纳米结构中的表面等离激元,由于其高度可塑性,可以调控表面等离激元特性,而在等离激元光子学中占据重要的地位。认识它,我们就能找到操纵表面等离激元的钥匙;运用它,我们就能打开表面等离激元应用新的大门。
[Abstract]:Surface isotherm is a mode of excitation caused by the coupling of charge density wave and surface electromagnetic wave bound to the surface of material and medium. The surface isotherm breaks through the diffraction limit propagation and increases the local electric field. The laser of specific wavelength can excite the surface isophosphors of certain materials, such as metal or graphene. Among them, the structure of metal nanowires can be used as a good carrier of surface isoexcitators. The two-dimensional graphene material has the adjustable properties of the surface isopitons and the smaller transmission loss, while the two dimensional graphene materials can support different surface isophosphoric modes, while the two dimensional graphene materials have the adjustable properties of the surface isopitons, It can be used for photoelectron information transmission and detection. The near-field properties of surface isoexcitations of one-dimensional metallic nanowires and one-dimensional graphene fold defects are studied. One-dimensional metal nanowire structures support both propagating and localized surface isoexcitators. The near field optical force on the surface of metal nanowires is confirmed by the motion of tiny particles in solution. By analyzing the motion state of nanocrystalline particles, we find the movement along the direction of the nanowires. Based on this, we use silver nanowires with different structures and laser to excite polarization. The motion of nanocrystalline particles can be controlled in a long distance direction. However, the surface of graphene has one dimensional fold defect, although its structure is small, it will affect the propagation of surface isotherm. We use scanning near-field optical microscopy. The near field optical imaging of graphene folds is realized. Through the analysis and numerical fitting of the actual spatial imaging, we find that the reflection effect caused by the fold morphology is very small. The main cause of the reflected surface isophosphorus wave is the change of photoconductivity at the fold. Furthermore, through the change of the fold characteristics, we can control the reflection effect of the surface isoexciton wave. The boundary and fold of graphene strip can reflect the surface iso-exciton wave. By using the scanning near-field imaging technique, we obtain the real space imaging under two superposition effects. It is found that the experimental results are combined with the theoretical analysis. For the fold of different types of photoconductive changes, the effect of superposition between them is completely opposite. The increase of photoconductivity will result in its comprehensive effect larger than that of simple boundary, that is, the length of coherent phase, and the decrease of photoconductivity will result in its comprehensive effect being smaller than that of simple boundary. That is to say, we can analyze and judge the optical and electrical properties of the fold by means of near-field optical imaging. We can control the properties of surface isopherons and play an important role in isophoric photonics. Knowing it, we can find the key to manipulate surface isopherons, and by using it, we can open a new door for the application of surface isopherons.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;O613.71

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