宽频太赫兹波功能器件关键技术研究

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摘要

电磁超材料的提出引领太赫兹波功能器件的发展向前迈进了一大步，由于这

类人工复合结构具有天然材料所不具备的超常电磁性质，它们的有效介电常数和

磁导率可以通过材料在关键物理尺寸上的结构有序设计来进行调控，所以它们往

往被利用来实现对电磁波性能的任意“剪裁”。然而由于传统的太赫兹波功能器件

大多采用金属谐振环式的电磁超材料结构，鉴于金属谐振环只能在谐振频率产生

特定的介电常数或磁导率，从而实现特定功能，这也就大大限制了太赫兹波功能

器件的工作带宽。

本文就两种具体的太赫兹器件：太赫兹龙伯透镜以及太赫兹吸收器，结合具

体的理论来拓宽它们的工作频宽，并通过仿真或实验的手段来验证我们的设计。

我们首先利用变换光学理论提出使用渐变折射率材料来实现龙伯透镜功能，然而

自然界并不存在折射率梯度变化的材料，我们由等效介质理论设计了一种亚波长

结构，以改变亚波长结构中空气孔的孔径的方式来实现折射率的梯度变化，并通

过排列周期性孔径渐变的亚波长结构从而实现宽频龙伯透镜的功能，我们还对这

种设计进行了理论仿真，仿真结果表明该太赫兹龙伯透镜的工作带宽达 1.25THz。

此外我们还根据光栅的衍射特性设计了一种太赫兹宽频吸收器，不同于以往基于

电磁超材料的太赫兹宽频吸收器只能通过多层谐振环的堆叠来实现较宽频吸收

的特性，我们所设计的宽频太赫兹吸收器结构简单，加工方便，且能够实现更宽

频的高效吸收，光栅层在低频时起到增透减反膜的功能，而在高频则通过衍射使

器件达到阻抗匹配条件从而实现反射率的降低，吸收率的提高。我们使用传统半

导体工艺对此吸收器进行加工，并利用太赫兹时域波谱系统对此吸收器的吸收特

性进行评估，实验证明该吸收器具有广角，偏振无关等特性，且能在 0.9THz-

2.1THz 范围内实现对能量高于 95%的吸收。我们在此基础上还提出了两种改进

方法，改变光栅结构或引入衬底干涉来使更多吸收峰加入到吸收谱中，从而生成

更宽的吸收谱。

综上，本文研究了两种太赫兹波宽频功能器件，它们都具有很大的应用前景，

对这些器件的研究与设计对以后设计其他宽频器件有着极重要的参考价值。

关键词：太赫兹宽频功能器件龙伯透镜吸收器

ABSTRACT

The advent of metamaterials has led the terahertz technology developing at a fast

pace, since this kind of artificial composite structure has the extraordinary

electromagnetic properties which natural materials don’t have. Their ability to

manipulate the effective permittivity and permeability through tuning the structure

make them widely used in the electromagnetic devices to arbitrarily tailor the

electromagnetic properties. However, since the traditional terahertz metamaterial

functional devices are mostly based on metallic resonator rings which only function at

their resonating frequencies, the working bandwidths of the functional devices are thus

greatly limited.

In this article, we will make discussions on two terahertz functional devices: the

terahertz Lüneburg lens and the terahertz absorber. We combined the specific theory to

enlarge their working bandwidth and also verified our design through the experiments

or the simulations. Firstly, we adopted the transformation optics theory and the effective

medium theory to realize the functionality of the Lüneburg lens. Because there is no

material with gradient refractive index in nature, we designed a subwavelength structure

which can achieve the gradient refractive index by changing the diameter of the air hole

inside it. These subwavelength structures were arrayed periodically to realize the

functions of the terahertz broadband Lüneburg lens. Simulation results showed that the

working bandwidth of such Lüneburg lens is up to 1.25THz. In addition, we also

designed a kind of terahertz broadband absorber based on the diffraction grating. Unlike

the traditional terahertz broadband absorber based on metamaterials which achieved a

relative wide absorption bandwidth through stacking several layers of metallic

resonator ring layers, our design is much more simpler and easier to fabricate. Besides

it can obtain an even wider absorption bandwidth. The grating layer in our design

functioned as an anti-reflection film in the lower frequency, while in the higher

frequency, the diffracted wave make the device fulfill the matching impedance

condition and eliminate the reflection. Those will enhance the absorbance for a wide

range of frequency. We also used the semiconductor technology to fabricate this

absorber. Its performance is evaluated by the terahertz time domain spectroscopy (THz-

TDS) system. The experimental results proved that the absorber is omnidirectional,

polarization independent and can attain an over 95% absorbance from 0.9THz to

2.1THz. Based on this research, we also found that by changing the structure of the

iii

gratings or introducing the interference of the substrate can merge more absorption

peaks into the absorption spectrum, which will increase the absorption bandwidth.

In summary, we studied two broadband terahertz functional devices, which all

have a large number of potential applications. The research and design of these devices

have an important values in designing other broadband functional devices.

Key words：Terahertz, Broadband functional devices, Lüneburg lens,

Absorber

中文摘要

ABSTRACT

第一章绪论 ................................................................................................................ 1

§1.1 引言 ............................................................................................................... 1

§1.2 太赫兹技术简介 ........................................................................................... 1

§1.3 国内外研究历史和现状 ............................................................................... 2

§1.4 本课题研究目的和意义 ............................................................................... 3

§1.5 本论文的主要内容 ....................................................................................... 3

第二章变换光学及等效介质理论 .............................................................................. 5

§2.1 变换光学理论简介 ....................................................................................... 5

§2.1.1 麦克斯韦方程组及其形式不变性 ....................................................... 5

§2.1.2 变换光学理论 ....................................................................................... 8

§2.2 等效折射率理论 ........................................................................................... 9

第三章宽频太赫兹龙伯透镜的设计 ........................................................................ 13

§3.1 龙伯透镜原理 ............................................................................................. 13

§3.2 宽频龙伯透镜的设计 ................................................................................. 15

第四章光栅型重掺杂硅基太赫兹宽频吸收器 ........................................................ 19

§4.1 吸收器发展史 ............................................................................................. 19

§4.1.1 单谐振环结构 .................................................................................... 19

§4.1.2 单层多谐振环结构 ............................................................................ 20

§4.1.3 多层多谐振环结构 ............................................................................ 21

§4.2 光栅型重掺杂硅基太赫兹宽频吸收器的设计 ......................................... 21

§4.2.1 德鲁德模型 ......................................................................................... 22

§4.2.2 吸收机制 ............................................................................................. 23

第五章宽频吸收器的加工测试及评估 .................................................................... 27

§5.1 光栅型重掺杂硅基太赫兹宽频吸收器的加工测试 ................................. 27

§5.1.1 光栅型重掺杂硅基太赫兹宽频吸收器的加工 ................................. 27

§5.1.2 光栅型重掺杂硅基太赫兹宽频吸收器的测试 ................................. 28

§5.2 光栅型重掺杂硅基太赫兹宽频吸收器吸收谱的讨论 .............................. 29

§5.2.1 光栅结构对吸收谱的影响 ................................................................. 29

§5.2.2 光栅结构对吸收谱的影响 ................................................................. 30

第六章光栅型太赫兹宽频吸收器的改进 ................................................................ 32

§6.1 引入更复杂的光栅结构 .............................................................................. 32

§6.2 引入更多的干涉机制 .................................................................................. 34

第七章总结和展望 .................................................................................................... 37

§7.1 主要结论 ..................................................................................................... 37

§7.2 未来展望 ..................................................................................................... 38

参考文献 ...................................................................................................................... 39

取得成果 ...................................................................................................................... 43

一、论文 ............................................................................................................. 43

二、专利 ............................................................................................................. 43

三、荣誉 ............................................................................................................. 43

结束语及致谢 .............................................................................................................. 44

附录 .............................................................................................................................. 46

A 专有名词对照表 ............................................................................................. 46

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摘要：

i摘要电磁超材料的提出引领太赫兹波功能器件的发展向前迈进了一大步，由于这类人工复合结构具有天然材料所不具备的超常电磁性质，它们的有效介电常数和磁导率可以通过材料在关键物理尺寸上的结构有序设计来进行调控，所以它们往往被利用来实现对电磁波性能的任意“剪裁”。然而由于传统的太赫兹波功能器件大多采用金属谐振环式的电磁超材料结构，鉴于金属谐振环只能在谐振频率产生特定的介电常数或磁导率，从而实现特定功能，这也就大大限制了太赫兹波功能器件的工作带宽。本文就两种具体的太赫兹器件：太赫兹龙伯透镜以及太赫兹吸收器，结合具体的理论来拓宽它们的工作频宽，并通过仿真或实验的手段来验证我们的设计。我们首先利用变换光学理论...

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