二维光子晶体中的反常折射现象及其应用研究
文献类型：学位论文
| 作者 | 唐志祥 |
| 学位类别 | 博士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 范滇元 |
| 关键词 | 光子晶体 左手材料 负折射 超透镜 |
| 其他题名 | Study of abnormal refraction in two-dimensional photonic crystal and its applications |
| 中文摘要 | 左手材料的特征是介电常数和磁导率同时为负值，它可以实现多种奇特的电磁现象如负折射、逆多普勒效应以及逆切伦柯夫效应等等。更重要的是，左手材料平板超透镜可以突破衍射极限。由于一直没有找到天然的左手材料，研究人员提出多种人工合成的方法，光子晶体就是其中之一。 光子晶体是一种折射率呈周期性变化的人工合成材料，电磁波在该材料中的传播受光子频带结构控制，在某些频率可以实现左手电磁现象如负折射、平板成像等等。归因于其可控的色散特性，光子晶体中的其它反常折射现象如自准直效应、超棱镜效应也相继被发掘。这些反常折射现象充分展示了光子晶体控制光子运动的能力，预示着光子晶体在未来光子学领域中的广阔应用前景，对高功率激光系统中的光束控制也有重要的应用潜力。 围绕这一国际科技界的研究热点，本论文着重研究二维光子晶体中的反常折射现象及其应用，取得一系列创新性成果。论文的主要内容如下： 1. 阐述光子晶体、左手材料以及负折射等基本概念，综述光子晶体和左手材料研究的发展现状和趋势；详细地介绍了光子晶体理论研究的三种数值计算方法即平面波展开法、多重散射法和时域有限差分法，并对平面波展开法进行改进以用于计算光子晶体等频线和群速度。 2. 深入地研究了平板成像的光子晶体物理模型，澄清了关于第一个光子晶体平板成像实验的理论纷争。研究表明，在实验频率范围内光子晶体有两个简并Bloch本征模，一个是被Parimi等人用来解释平板成像的左手模，另一个则是被疏漏的右手性自准直本征模。色散分析和多重散射仿真结果一致表明，实验所观察到的所谓“光子晶体平板成像”并不是左手电磁现象，而是两简并Bloch模被点源同时激发在光子晶体近场相干叠加的结果。由于近场对表面细节非常敏感，点源的移动导致近场场强分布发生剧烈变化如所谓的像点消失。 3. 系统地研究二维正方格光子晶体在不完全带隙的各向异性，总结出各向异性导致的三种反常折射及平板成像规律。第一种是所谓的正折射平板近场成像。研究表明这只是电场(或磁场)分布的一种假象，场强分布清晰地表明平板后并不成像！第二种是典型的自准直效应。紧靠平板的点源发出的电磁波可以隧穿平板在另一界面附近亚波长成像。最后一种类似于光疏左手材料的负折射和平板成像。 4. 成功设计多种具有左手电磁特性的二维光子晶体如三角格介质椭圆柱光子晶体、蜂窝格光子晶体、正方格和三角格介质管光子晶体等。其中正方格介质管光子晶体的Bloch波可以在两个高对称面有效地被激发，因此没有界面选择限制。此外，这种介质管光子晶体有望借助光子晶体光纤成熟的制备工艺实现光波段左手材料的批量生产。 5. 探索基于光子晶体反常折射特性的实际应用，提出并设计了两种新型空间滤波器，研究验证了低通滤波能力。其中一种是左手性光疏光子晶体，另一种是工作在自准直频率的正方格光子晶体。 6. 最后对全文工作做出总结，指出目前研究存在的问题，并展望今后需要进一步开展的工作。 |
| 英文摘要 | Left-handed Material (LHM) is characterized by simultaneous negative permittivity and permeability. Unusual electromagnetic (EM) phenomena such as negative refraction, reversed Doppler shift and reversed Cerenkov radiation could be expected in LHMs. More importantly, a flat superlens made of LHM can overcome the diffraction limit. Due to the absence of nature materials with both negative permittivity and permeability, various approaches have been proposed to fabricate the equivalent meta-material. Photonic crystal (PhC) is one of them. PhC is an artificial medium whose refractive index is periodically arranged. EM waves propagated in this medium are controlled by the photonic band structure. In some frequency range, left-handed phenomena such as negative refraction and flat slab imaging can be achieved. Due to its controllable dispersion characteristics, other abnormal phenomena such as self-collimating effect and superprism effect have been discovered in PhCs one after the other. Due to its ability to control the photons, these abnormal refractions have broad applications not only in photonics domain in the future, but also in control of laser beams in high-power laser systems. Surrounding this international hot spot in scientific and technical research, the thesis has put emphasis on studying the abnormal refraction and its applications in two-dimensional (2D) PhCs, and achieved a series of innovative results. Main contents of the thesis are summarized as follows: 1. Some basic concepts such as PhC, LHM and negative refraction have been presented simply. Present situation and development trends of the research on PhC and LHM have been summarized. Three methods for theoretical study on PhC have been described in details. They are plane-wave expansion (PWE) method, multiple scattering method (MSM) and finite-difference time-domain (FDTD) method. In order to calculate the equifrequency surfaces and group velocities of PhCs, the standard PWE method has been revised. 2. The PhCs used to demonstrate flat slab imaging experimentally have been studied thoroughly. Some debates on the experiment results have been clarified. Systematical investigation indicates that there are two degenerated Bloch modes for the PhC in the experimental frequency range. One of them is a left-handed mode that has been used to explain the flat slab imaging by Parimi. The other is a right-handed self-collimating mode, which have been neglected before. Both the dispersion analysis and numerical simulations have demonstrated that the so-called image observed in the experiment is not a left-handed EM phenomenon but a coherent near-filed superposition of these two degenerate Bloch modes excited by a point source simultaneously. Because the near field is sensitive to the surface details, displacement of the point source results in dramatic changes of EM intensity in the near field, such as the disappearance of the so-called image. 3. Anisotropy of a 2D square-lattice PhC has been investigated systematically in the partial band gap. Three kinds of abnormal refraction and its resulted flat focusing have been summarized. The first is the so-called positive refraction and its resulted near-field flat slab focusing. The research results have indicated that it is a fake presentation resulted from the electric (or magnetic) field distributions. EM intensities demonstrate clearly that no image is formed. The second is a typical self-collimating effect. EM waves emitted from a point source that is located near the PhC slab can tunnel through the slab and form a subwavelength image near the other interface. The last is similar to the negative refraction and flat slab focusing resulted from the optical thinner LHMs. 4. Several kinds of left-handed PhC, such as triangle lattice dielectric elliptical- rod PhC, honeycomb lattice PhC, square and triangle lattice dielectric-tube PhC have been designed. The interface limitation does not exist for the square-lattice dielectric-tube PhC because its Bloch modes can be excited effectively at its two symmetrical interfaces. Moreover, borrowing ideas from the sophisticated manufacturing engineering of the PhC fiber, it is possible to fabricate this dielectric-tube PhC to realize mass-production of LHM operated at optical frequency. 5. Applications of abnormal refraction in PhC have been searched after. A new style low-pass spatial filter is proposed. Two kinds of PhCs are designed to verify the ability of low-pass spatial filtering. One of them is an optical thinner left-handed PhC. The other is a 2D square-lattice PhC operated at the self-collimating frequency. 6. Finally, main achievements of the dissertation are summarized, and some problems in current research are present. Which should be done in the future is prospected too. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15323]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 唐志祥. 二维光子晶体中的反常折射现象及其应用研究[D]. 中国科学院上海光学精密机械研究所. 2007. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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