表面等离子体近场成像的有限元法模拟与分析

发布时间：2018-05-05 19:04

本文选题：表面等离子体耦合 + 近场增强　；参考：《清华大学》2016年博士论文

【摘要】：金属纳米结构的表面等离子体的耦合可以产生巨大的局域电场增强。作为表面等离子体光子学领域最引人注目的现象之一,近场增强是许多应用的基础,从表面增强光谱、生物化学传感器,到单分子检测、非线性光学等等。本文以表面增强拉曼散射的电磁增强机理为切入点,在电磁学有限元法的基础上,应用高斯定律,发展了一种直观的表面等离子体近场成像方法,可以直接确定复杂的表面等离子体共振模式。随后,从实际应用中提取出了一系列典型的表面等离子体共振体系,围绕表面等离子体共振模式的耦合、近场增强的特性以及近场和远场共振的光谱偏移等基本理论问题,进行系统而深入的有限元法模拟计算研究,旨在提供清晰的表面等离子体物理图像,促进表面等离子体器件的优化设计和光谱学应用。对于最重要的电磁热点结构:纳米颗粒二聚体,本文定量地分析了其纳米狭缝效应,发现近场增强几乎按纳米狭缝尺寸的幂律形式衰减,同时近场和远场共振位移都遵循狭缝尺寸的单指数衰减方程。当狭缝区域被金属桥连接导通以后,可见光区域的成键偶极子模式迅速衰退,但却能激发电荷转移模式,产生巨大的可调制的红外近场增强,为红外波段潜在的器件提供了一个新的结构设计思路。对于纳米颗粒二聚体的替代结构:金属镜膜耦合的纳米颗粒体系,本文考虑了纳米颗粒-纳米颗粒和纳米颗粒-镜膜两种耦合作用同时存在时系统共振模式和近场增强的变化,证明金属镜膜会诱导出两种不同的成键偶极子模式,能提供比孤立的成键偶极子模式更强的局域电场增强。对于备受关注的金属纳米阵列结构,本文预测了二维表面等离子体晶体的具有普遍性的法诺共振近场相长和相消的干涉花样,以最直观的方式证明了其物理本质是一种波的干涉现象。最后,基于以上研究结果和理论认识,本文研究了亚波长密排金纳米棒阵列。通过远场和近场光学性质的理论计算,并结合实验验证,证明了阵列多极子耦合模式的存在及其可调制性。
[Abstract]:The coupling of surface plasmas in metal nanostructures can result in a large local electric field enhancement. As one of the most attractive phenomena in the field of surface plasmon photonics, near field enhancement is the basis of many applications, from surface enhanced spectroscopy, biochemical sensors, single molecule detection, nonlinear optics and so on. Based on the electromagnetic enhancement mechanism of surface-enhanced Raman scattering and on the basis of electromagnetic finite element method and Gao Si's law, an intuitionistic near-field imaging method for surface plasmas is developed in this paper. Complex surface plasmon resonance modes can be determined directly. Then, a series of typical surface plasmon resonance systems are extracted from practical applications, which revolve around the coupling of surface plasmon resonance modes, the characteristics of near-field enhancement and the spectral offset of near-field and far-field resonance. The purpose of this paper is to provide clear physical images of surface plasmas and to promote the optimal design and spectroscopic applications of surface plasma devices. For the most important hot electromagnetic structure: nanocrystalline dimer, the effect of nanometer slit is quantitatively analyzed. It is found that the near field enhancement attenuates almost according to the power law of nanometer slit size. At the same time, both near-field and far-field resonance displacements follow the single exponential attenuation equation of slit size. When the slit region is connected by a metal bridge, the bonding dipole mode in the visible region decays rapidly, but it can excite the charge transfer mode, resulting in a huge modulated near infrared enhancement. It provides a new structure design idea for infrared band potential devices. For the alternative structure of nanocrystalline dimer: metal mirror membrane coupled nanocrystalline system, the system resonance mode and near-field enhancement changes are considered when both nanocrystalline and nanocrystalline nanomicroscopic coupling exist at the same time. It is shown that the metal mirror film can induce two different bonding dipole modes, which can provide a stronger local electric field enhancement than the isolated bonding dipole mode. For the metal nanoarrays which have attracted much attention, the interference patterns of the universal near field Farno resonance phase and elimination of two-dimensional surface plasma crystals are predicted in this paper. It is proved in the most intuitionistic way that its physical essence is a wave interference phenomenon. Finally, based on the above research results and theoretical understanding, we studied the subwavelength dense gold nanorods array. Through the theoretical calculation of the optical properties of the far and near fields and the experimental verification, the existence and modulability of the array multipole coupling mode are proved.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG111

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