含特异材料光子晶体中单向传输机制及其时延特性研究

The unidirectional transmission (also called non-reciprocal transmission) of electromagnetic (EM) wave possesses the similar functionality being transferred only in the forward direction as electric diodes. Such unique physical phenomenon has been widely used in device design, such as circulators and isolators, in optical communications and military affairs. In recent years, photonic crystals (PCs) and metamaterials emerge with great wonderment. The rich dispersion properties of PCs and the designable nature of metamaterials have shown attractive foreground in Condensed Matter Physics and Optics. In this project, we propose to construct PCs with artificially designed metamaterials, and study the unidirectional transmission mechanism and delay characteristics of such structures by using effective medium theory (EMT) and Finite-Difference Time-Domain (FDTD) method. The main research contents are as follows: (1) the existence conditions and the physical mechanism of unidirectional transmission for PCs containing different kinds of metamaterials; (2) to design an optimized unidirectional waveguide based on the above research, and then study the steady transmission characteristics of monochromatic EM wave, as well as the delay characteristics affected by different kinds of defects. This project will not only provide new ideas for the realization of unidirectional transmission under small-scale, but also can provide theoretical basis for new types of integrated delay devices in the future.

电磁波单向传输（又称非互易传输）具有类似于电子二极管的“正向导通，反向截止”的功能，这种奇特的物理现象被广泛应用于光通信、军事等领域中的单向器件设计中，如环形器、隔离器等。近年来，光子晶体和特异材料异军突起，前者丰富的能带特性和后者电磁参数的可灵活设计性使得它们在凝聚态物理、光学等领域中展现出极其诱人的前景。本项目提出将人工设计的特异材料引入光子晶体，利用有效介质理论和时域有限差分等方法来探索该类结构中单向传输的物理机制及其时延特性。主要内容包括：(1)从理论上探索含不同类型特异材料光子晶体中单向传输的存在条件和物理机制；(2)在上述基础上优化设计一种微结构单向波导，研究电磁波在该单向波导中的稳态传输性质，并进一步探讨不同缺陷对单向波导的时延特性的影响。本研究不仅为微小尺度下实现单向传输提供新的思路，而且也为今后发展可集成的新型时延光子器件提供理论依据。

光子晶体和特异材料(也称超材料)是两类重要的人工电磁材料，它们存在单向传输、超准直、超棱镜等一系列新颖的物理效应，光子晶体复杂的能带特性和特异材料丰富的电磁参数使得它们在凝聚态、光学等领域中展现出诱人的前景。本项目提出结合光子晶体和特异材料实现微小尺度下的单向传输，主要研究了光子晶体的单向传输物理机制、时延特性、反常光传输性质及其应用。主要成果如下：(1)研究了特异材料光子晶体中单向传输的实现机制和存在条件，结果显示通过强耦合作用打破结构的时间反演对称性可获得单向传输模；(2)研究了线缺陷对单向波导时延特性的影响，发现相位延时对缺陷折射率的变化较为敏感，但对厚度变化不敏感，进一步利用单向波导设计了一种三端口环行器；(3)发现了一维光子晶体独特的π透射相移特性，该相位特性可用于设计二进制差分相移键控(2DPSK)调制器等相位器件；(4)突破了超棱镜效应主要用于波长分离和角度分离的传统思路，联合超准直和超棱镜效应，实现了能量比可实时、连续调节的大角度光分束器。本项目的研究成果不仅为单向传输的实现提供了新的思路，而且丰富了光子晶体和特异材料的研究内容，在许多方面都具有潜在的应用价值。