贵金属纳米颗粒聚合体中多重法诺共振效应的研究
发布时间：2018-07-31 15:38
【摘要】：金属纳米颗粒的局域表面等离激元共振时能够呈现出独特的电磁场增强和消光效应，入射光能量能被强烈局域在金属表面，利用这局域特性可突破光的衍射极限，已经受到越来越多研究者的关注。当两个或更多的金属纳米颗粒紧密放置构成复杂纳米结构时，金属纳米颗粒间的等离激元可以通过近场相互作用进行耦合，从而产生一系列的等离激元杂化。合理的设计纳米颗粒的放置方式及控制颗粒间的近场耦合，在复杂纳米结构中就能展现出像法诺共振干涉效应。对于表面等离激元体系中法诺共振不仅能够有效降低体系辐射衰减，还能将入射光能量更好的局限在结构表面的性质，使得光谱更加精细，并可产生更大的局域场增强，提高体系的传感性能和非线性效应。与单一法诺共振相比，多重法诺共振效应的体系可在多个波段可以同时调制光谱，有利于实现可控的谱线整形，调整多重法诺共振峰位与之匹配，能在多个波段处同时产生较大的局域场增强，从而极大提高表面增强拉曼散射的增强因子，当多重法诺共振与不同分子振动谱形成匹配，可以实现不同分子的高效检测。因此复杂纳米结构中的法诺共振被广泛应用于生物传感、光学开关、表面增强拉曼散射等领域。 本论文是基于贵金属纳米颗粒的局域表面等离激元共振的特性，利用时域有限差分法数值模拟研究了几种复杂金属纳米结构中的多重法诺共振现象。主要工作包括： (1)研究了纳米环四聚体和八聚体中的法诺共振现象，分析了相应的近场分布，讨论了纳米环四聚体和八聚体中法诺共振现象形成的原因，以及通过调整纳米环间夹角和间距的大小，对法诺共振的光谱位置和调制深度进行调谐。利用劈裂纳米环的偶极共振模式与四极共振模式的能隙很小的特点，同时讨论了劈裂纳米环四聚体和八聚体的光学性质，结果表明相比于纳米环四聚体和八聚体，在劈裂纳米环四聚体和八聚体中能产生更多的法诺共振，相同地调整纳米环间夹角和间距的大小，能对法诺共振的光谱位置和调制深度有更大的调谐。 (2)利用简单地改变入射光偏振方向就能控制L型纳米棒的光谱特性和近场分布这一特点，，研究了两种L型纳米棒二聚体在不同入射光偏振角时的光学性质，并在此基础上构建了复合纳米棒结构和L型纳米棒四聚体两种复杂结构，研究结果表明，复合纳米棒结构中能够产生双重的法诺共振现象，通过改变纳米棒长度可以对结构中的法诺共振进行调制，并且可以将结构分解成L型纳米棒二聚体和普通纳米棒二聚体两个部分，通过对比这两种二聚体共振峰位置随纳米棒长度的变化关系，可直观的了解复合纳米棒结构中消光光谱的变化。另外对L型纳米棒四聚体研究发现，由于其结构的旋转对称性，其远场性质不随入射光偏振方向变化而改变，当改变纳米棒长度破坏其结构对称性和改变入射光偏振方向时，四聚体中最多能出现三重的法诺共振。
[Abstract]:The local surface of the metal nanoparticles can show unique electromagnetic field enhancement and extinction effect. The incident light energy can be strongly localized on the metal surface. Using this local characteristic can break through the diffraction limit of the light, more and more researchers have paid attention to it. When two or more metal nanoparticles are closely placed. When the complex nanostructures are made up, the plasmons between the metal nanoparticles can be coupled through the near field interaction, resulting in a series of plasmons. A reasonable design of the nanoparticles and the control of the near field coupling between the particles can show a Fano resonance interference effect in the complex nanoscale structure. In the surface plasmon resonance system, the Fano resonance can not only effectively reduce the radiation attenuation of the system, but also limit the energy of the incident light to the properties of the structure surface, which makes the spectrum more fine, and can produce a larger local field enhancement, and improve the sensing and non linear effects of the system. The system of resonance effect can modulate the spectrum at the same time in multiple bands. It is beneficial to realize controllable spectral line shaping and adjust the matching of multiple Fano resonance peaks. It can produce large local field enhancement at multiple bands at the same time, thus greatly improving the enhancement factor of surface enhanced Raman scattering, when multiple Fano resonance and different molecular vibration are used. The dynamic spectrum matching can achieve high efficient detection of different molecules. Therefore, Fano resonance in complex nanostructures is widely used in the fields of biosensing, optical switch, surface enhanced Raman scattering and so on.
This paper is based on the characteristic of local surface plasmon resonance of noble metal nanoparticles. The multiple Fano resonance phenomena in several complex metal nanostructures are studied by the finite difference time domain method. The main work includes:
(1) the Fano resonance phenomenon in the nano-ring four polymer and eight polymer was studied. The corresponding near field distribution was analyzed. The reasons for the formation of the Fano resonance in the nano-ring four polymer and the eight polymer were discussed, and the spectral position and the modulation depth of the Fanno co oscillator were tuned by adjusting the angle and spacing between the nanoscale rings. The optical properties of the split nano ring four polymer and the eight polymer are discussed at the same time in the dipole resonance mode and the quadrupole resonance mode. The results show that the nano ring four polymer and the eight polymer can produce more Fano resonance in the split nano-ring four polymer and eight polymer, and adjust the nanoscale interclips in the same way. The size of the angle and spacing can further adjust the spectral location and modulation depth of the Fano resonance.
(2) by simply changing the polarization direction of the incident light, the spectral and near field distribution of the L nanorods can be controlled. The optical properties of the two L nanorods with different incident light polarization angles are studied. On this basis, the structure of the composite nanorods and the two complex structures of the L nanorod four polymer are constructed. The results show that the composite nanorod structure can produce a double Fano resonance phenomenon. By changing the length of the nanorods, the Fano resonance in the structure can be modulated, and the structure can be decomposed into two parts of the L type nanorod two polymer and the ordinary nanorod two polymer. By comparing the two two polymer resonance peaks with the nanorod length The variation of the extinction spectra in the structure of the composite nanorods can be understood intuitively. In addition, the study of the four polymer of the L nanorods shows that the far-field properties of the nanorods are not changed with the polarization direction of the incident light, and the structure symmetry of the nanorods and the polarization direction of the incident light are changed when the length of the nanorods is changed. At the time, the three fold of the four polymer can be observed.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O631
本文编号：2156032
[Abstract]:The local surface of the metal nanoparticles can show unique electromagnetic field enhancement and extinction effect. The incident light energy can be strongly localized on the metal surface. Using this local characteristic can break through the diffraction limit of the light, more and more researchers have paid attention to it. When two or more metal nanoparticles are closely placed. When the complex nanostructures are made up, the plasmons between the metal nanoparticles can be coupled through the near field interaction, resulting in a series of plasmons. A reasonable design of the nanoparticles and the control of the near field coupling between the particles can show a Fano resonance interference effect in the complex nanoscale structure. In the surface plasmon resonance system, the Fano resonance can not only effectively reduce the radiation attenuation of the system, but also limit the energy of the incident light to the properties of the structure surface, which makes the spectrum more fine, and can produce a larger local field enhancement, and improve the sensing and non linear effects of the system. The system of resonance effect can modulate the spectrum at the same time in multiple bands. It is beneficial to realize controllable spectral line shaping and adjust the matching of multiple Fano resonance peaks. It can produce large local field enhancement at multiple bands at the same time, thus greatly improving the enhancement factor of surface enhanced Raman scattering, when multiple Fano resonance and different molecular vibration are used. The dynamic spectrum matching can achieve high efficient detection of different molecules. Therefore, Fano resonance in complex nanostructures is widely used in the fields of biosensing, optical switch, surface enhanced Raman scattering and so on.
This paper is based on the characteristic of local surface plasmon resonance of noble metal nanoparticles. The multiple Fano resonance phenomena in several complex metal nanostructures are studied by the finite difference time domain method. The main work includes:
(1) the Fano resonance phenomenon in the nano-ring four polymer and eight polymer was studied. The corresponding near field distribution was analyzed. The reasons for the formation of the Fano resonance in the nano-ring four polymer and the eight polymer were discussed, and the spectral position and the modulation depth of the Fanno co oscillator were tuned by adjusting the angle and spacing between the nanoscale rings. The optical properties of the split nano ring four polymer and the eight polymer are discussed at the same time in the dipole resonance mode and the quadrupole resonance mode. The results show that the nano ring four polymer and the eight polymer can produce more Fano resonance in the split nano-ring four polymer and eight polymer, and adjust the nanoscale interclips in the same way. The size of the angle and spacing can further adjust the spectral location and modulation depth of the Fano resonance.
(2) by simply changing the polarization direction of the incident light, the spectral and near field distribution of the L nanorods can be controlled. The optical properties of the two L nanorods with different incident light polarization angles are studied. On this basis, the structure of the composite nanorods and the two complex structures of the L nanorod four polymer are constructed. The results show that the composite nanorod structure can produce a double Fano resonance phenomenon. By changing the length of the nanorods, the Fano resonance in the structure can be modulated, and the structure can be decomposed into two parts of the L type nanorod two polymer and the ordinary nanorod two polymer. By comparing the two two polymer resonance peaks with the nanorod length The variation of the extinction spectra in the structure of the composite nanorods can be understood intuitively. In addition, the study of the four polymer of the L nanorods shows that the far-field properties of the nanorods are not changed with the polarization direction of the incident light, and the structure symmetry of the nanorods and the polarization direction of the incident light are changed when the length of the nanorods is changed. At the time, the three fold of the four polymer can be observed.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O631
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本文编号：2156032
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