论文总字数：25949字

摘 要

利用COMSOL仿真软件，模拟了1550nm入射光下波导横截面内基模的场分布，计算了Z向时均功率。通过改变波导的结构参数，得到波导的光传输特性。我们发现:该结构光波导能将光场有效的约束在纳米管的空腔内；有效折射率的实部随着纳米管内侧宽度的增加而减小，随着纳米管外侧宽度和纳米管折射率的增加而增大，随着银层厚度的增加先减小后趋于稳定；有效折射率的虚部随着纳米管内侧宽度和银层厚度的增加先减小后趋于稳定，随着纳米管外侧宽度的增加而减小，随着纳米管折射率的增加先减小后增大；表面等离子激元的传输距离随着纳米管内侧宽度和银层厚度的增加先增大后趋于稳定，随着纳米管外侧宽度的增加而增大，随着纳米管折射率的增加先增大后减小。

研究该结构波导传输的频率特性后发现:入射光波长处于红外波段时，波导内能形成空腔内模。而在可见光、紫外光波段，难以形成有效的腔内模;有效折射率实部和虚部大体上表现为随入射波长的增加而减少,传输距离大体上表现为随入射波长的增加而增大。只是在300~400nm入射光内形成了其他形式的模场，使频率特性表现出数值上的跳变。

比较四种不同金属构建的ZnO纳米管光波导的模场，分析结果表明：金、银、铜、铝构建的波导在1550nm、885.6nm的入射光下场分布相似，都能形成空腔内模，其中在银构建的波导中传输损耗较小；不同于金、银、铝三种金属，铜构建的波导在可见光、紫外光波段表现效果较好，能有效的约束光场。

为了可以得到理想的模式分布，以圆柱形纳米管取代六方纳米管，模场分析表明：夹在银层间的圆柱纳米管波导的模场难以被约束到空腔内；包裹在银层间的圆柱纳米管波导虽然可以约束模场到空腔内，但波导的传输损耗较大。

关键字：表面等离子激元光波导;ZnO纳米管;模场分布;传输损耗

A STUDY ON THE OPTICAL TRANSMISSION PROPERTIES OF ZnO NANOTUBE

FIBER WAVEGUIDES

06012226 Li Xun

Supervised by Wu Xufeng

Abstract: This paper summarizes the research status of the surface plasmon polaritons waveguide and introduces the basic theory of surface plasmon polaritons. On the basis of this, we propose a kind of surface plasmon polaritons waveguide that consists of a zinc oxide nanotube and a metal layer.

Then we simulate the field distribution of the fundamental mode under 1550nm incident light by using COMSOL. In addition, we calculate the average power in Z direction. Next we change the structure parameters of fiber waveguide, and get the optical transmission characteristics. We find that the optical waveguide can restrain the light field into the cavity of the nanotube effectively; For the real part of effective refractive index, it reduces with the increase of the inside width, it increases with the increase of the outside width and the refractive index of nanotube, and the increasing thickness of the silver layer can make it decrease and then tend to stable; For the imaginary part of effective refractive index, the increasing inside width and thickness of the silver layer can make it decrease and then tend to stable, it decreases with the increase of the outside width, and it decreases and then increases with the increase of the refractive index of nanotube; For the transmission distance of surface plasmon polaritons, the increasing thickness of the silver layer and inside width can make it decrease and then tend to stable, it increases with the increase of the outside width, and it first increases then decreases with the increase of the refractive index of nanotube.

After the study of the frequency characteristics, we find that cavity inner mold can be formed in the waveguide when the incident light wavelength is in the infrared wave band, but it is hard to form cavity inner mold in the visible band and ultraviolet band. The real part and imaginary part in effective index of refraction decrease with the increase of incident wavelength in principle, and the propagation distance increases with the increase of the incident wavelength in principle. Just because other modes are formed in the range of 300nm and 400nm, and that make the frequency characteristics show some numerical jumps.

Comparing with the mode field distribution of the optical waveguide which is composed of four different metal layers, we conclude that the field distribution of four kinds of waveguide is similar in 1550nm and 885.6nm, all can form cavity inner mold, and the transmission loss of the waveguide that consists of silver layer is slightly smaller. Comparing with the other three kinds of metal, the waveguide composed of copper layer can constrain the light field effectively in the visible band and ultraviolet band.

In order to obtain the ideal mode distribution, we replace the hexagonal nanotube by the cylindrical nanotube. We find that is difficult to restrain the mode field into the cavity when the cylindrical nanotube is sandwiched between the silver layers; the mode field can be bound into the cavity by using the cylindrical nanotube that is wrapped in silver layer, but that causes a large transmission loss to waveguide.

Key words: the surface plasmon polaritons waveguide; ZnO nanotube; mode field distribution; transmission loss

目录

摘要 I

Abstract II

第一章 绪论 1

1.1 研究背景及意义 1

1.1.1 研究背景 1

1.1.2 研究意义 1

1.2 表面等离子激元光波导的研究现状 1

1.3 ZnO作为光波导的研究进展 4

1.4 ZnO作为表面等离子激元光波导的科研进展 5

1.5 本文的主要研究内容 7

第二章 表面等离子激元基础理论 8

2.1 表面等离子激元的概念 8

2.2 Maxwell方程组 8

2.3 Drude模型 9

2.4 表面等离子激元的特性 10

2.4.1 色散关系 10

2.4.2 特征参数 13

2.5 本章小结 16

第三章 ZnO纳米管光波导 17

3.1 引言 17

3.2 ZnO纳米管光波导的结构 17

3.3 1550nm入射光下ZnO纳米管光波导的传输特性 18

3.3.1 基模的电场模分布 18

3.3.2 波导参数对传输特性的影响 19

3.3.3 Z向时均功率 23

3.4 不同入射波长下ZnO纳米管光波导的传输特性 25

3.4.1 基模的电场模分布 26

3.4.2 光波导的频率特性 26

3.5 不同金属层构建的光波导 28

3.6 圆柱形纳米管构建的光波导 30

3.7 本章小结 31

第四章 总结与展望 32

致谢 34

参考文献: 35

第一章 绪论

1.1 研究背景及意义

1.1.1 研究背景

19 世纪，麦克斯韦建立了经典的电磁场理论。自此之后，人类以此为基础，对有线通信、无线通信进行了技术革新，对人类的生活和科技技术产生了巨大的影响。

随着时代的进步，社会信息化程度不断提高，人类对于信息处理速度的要求也越来越高，这时，现有的电子学技术就受到了限制。由于光子器件具有高速率、大带宽、良好的信号屏蔽、低发热的优点，人们对用光子器件传输信息的想法日益迫切。然而遗憾的是，传统的光子器件因为存在衍射极限的问题，导致其尺寸只能维持在微米量级，无法在纳米芯片上施展高速率的优势。

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