摘 要

通常的光栅，无论是透射型还是反射型光栅都具有如下特点：零级衍射光强最强，但不是色散的；一级衍射虽然是色散的，但光强很弱。本文通过使用CST STUDIO SUITE（电磁仿真软件）研究二维金属-绝缘体-金属三明治结构的金属纳米块阵列的反常衍射现象。系统的上层结构为矩形纳米块阵列，中间层为玻璃介质，下层为贵金属层。其单胞在一个方向上是亚波长的，而在与之垂直的方向是超波长的，形成一个超波长-亚波长的表面等离激元结构。其衍射光具有如下特点：零级衍射和一个一级衍射被强烈抑制，光强非常弱；而另一个一级衍射光强却非常强，衍射效率在测量的波长范围内超过50%；这一反常衍射现象预计可以应用到分光计中作为光的色散器件。本课题的研究目标是：纳米金属块的尺寸效应对其反常衍射的影响。即：纳米金属块的长、宽和厚度以及玻璃层的厚度等因素是如何影响反常衍射效应的。

关键词：亚波长 等离激元 超波长 尺寸效应 反常衍射

The Size Effect of Ultra Wavelength – Sub Wavelength Metal Nano-blocks

ABSTRACT

The normal grating, either transmissive or reflective grating type has the following characteristics:Zero order diffraction light intensity is the strongest but dispersive.Although the first order diffraction is dispersive,light intensity is weak.This article through the use of CST STUDIO SUITE research two-dimensional metal-insulator-metal anomalous diffraction phenomenon of metal nano block array of sandwich structure.The upper structure of the system is rectangular nano block array,the intermediate is glass medium,the lower layer is precious metal layer.The single cell is a sub-wavelength in one direction.and in the direction of the vertical is ultra - wavelength.then a surface plasmon structure with a ultra-wavelength and sub-wavelength is formed.The diffraction light has the following characteristics:the zero order diffraction and a first-order diffraction were strongly suppressed,and the light intensity is very weak.However the other one is very strong,the diffraction efficiency is more than 50% in the wavelength range of the measurement.This anomalous diffraction phenomenon is expected to be applied as a dispersion device light spectrometer.The goal of this research is that the effect of the size effect of nano metal block on the anomalous diffraction.Namely,the length, width and thickness of the nano metal block and thickness of glass layer are how to affect the effect of anomalous diffraction.

Key Words: Sub-wavelength.; Plasmon excitation.; Ultra - wavelength.; Size effect.; Anomalous diffraction.

目 录

摘 要........................................................................................................Ⅱ

ABSTRACT.............................................................................................Ⅲ

1. 引言..............................................................................................1
2. CST软件的使用及模型设计......................................................3

2.1 设置适用单位...................................................................................................3

2.2 设置背景材料...................................................................................................3

2.3 设置材料种类...................................................................................................4

2.4 设置结构参数...................................................................................................6

2.5 画元胞结构图...................................................................................................7

2.6 设置边界条件...................................................................................................8

2.7 设置激励源.......................................................................................................8

2.8 设置探针...........................................................................................................9

2.9 设置频率范围...................................................................................................9

2.10 运行计算.........................................................................................................9

2.11 查看透射谱...................................................................................................10

2.12查看场分布.....................................................................................................11

2.13输出场分布.....................................................................................................11

2.14多周期显示.....................................................................................................11

2.15操作撤销.........................................................................................................11

1. 三明治结构的金属纳米块阵列的反射谱...............................12
2. 结论............................................................................................20

参考文献..................................................................................................21

1. 引言

基于能带理论和半导体工艺的微电子技术极大地促进了人类社会的发展，也极大地改变了人们的生活方式。不过，当电子元件的尺寸小到一定程度时，量子效应却限制了微电子技术的进一步发展。与此同时，人类知识的增长以及信息量的急速膨胀要求进一步提高信息的传输效率。我们知道，作为信息的载体，光子优于电子；然而在集成上，光子元件却输于电子元件。这是由于光的衍射效应的存在，使得介电光学元件的尺寸受到了极大的限制（至少为波长的一半）。比如，当前对电磁波的传播进行约束和操纵的一个重要途径是利用光波导以及Bragg 反射型光子带隙材料[1-2]。对于前者如单模光纤，其尺寸通常为若干微米；对于后者即光子晶体，其大小亦至少为若干个波长。因此，研究和利用亚波长结构来控制电磁波的传播具有重要的实际意义。

那么如何能利用亚波长结构来控制电磁波的传播呢？实际上，Bragg 反射仅是问题的一个方面，同时它也并非形成能带结构的唯一机制。我们知道，电磁波在材料中的传播过程，其实质就是带电粒子与电磁场相互作用的过程，也是电磁波与材料极化波的耦合过程。在强场的情况下，光与非线性极化波的强烈耦合将导致（准）相位匹配的频率转换。而在线性情况下，电磁波与材料线性极化波的耦合模被称为极化激元（狭义的极化激元仅限于共振频率附近的耦合模）[3-6]。比如，光子与金属表面等离激元可耦合形成表面等离极化激元，光子与晶格振动的横光学声子可耦合产生声子极化激元。它们的产生可伴随着光子能隙以及亚波长的结构特征。

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