基于磁光子晶体的磁控可调谐太赫兹滤波器和开关

本文研究了铁氧体磁性材料应用于太赫兹波导器件的可行性. 利用铁氧体磁性材料的磁导率随外磁场改变而变化的性质,设计出了一种新颖的磁控连续可调谐太赫兹滤波器和开关. 利用平面波展开法(plane wave expansion,PWE)和时域有限差分法(finite difference time domain,FDTD)计算了二维磁光子晶体中外磁场变化对带隙位置和宽度的影响,结果显示应用该结构实现的滤波器和开关具有良好的性能. 关键词： 磁光子晶体 铁氧体 太赫兹     

二维复式晶格完全带隙光子晶体缺陷频率的分析

提出了一种具有完全带隙的二维复式晶格光子晶体,该晶体是在二维正方形格子中,旋转截面为正方形的柱子,同时在每个原胞中心引入圆形截面的柱子而形成的,并在其中引入点缺陷。运用平面波展开法并结合超晶胞理论分析此缺陷态光子晶体的频率特性。仿真结果表明,通过调节缺陷的尺寸、角度等结构参量,可以改变缺陷态频率的位置,使TE和TM模缺陷态频率一致,TE模和TM模同时谐振,处于缺陷态频率的入射光就能够完全耦合进点缺陷,具有较高的耦合效率。这种结构的复式晶格完全带隙光子晶体为制作完全带隙光子晶体谐振腔提供了理论基础。     

二维正方格子磁性光子晶体的界面传导模

采用平面波展开加超元胞方法计算了二维正方格子磁性光子晶体的光子带隙结构，其中散射子的形状分别为长方形，正方形，六角形和圆形.结果表明绝对带隙宽度和其宽高比远大于同种结构的非磁性光子晶体.在此基础上，构成了混合型异质结，并计算了相应的传导模，发现了理想的界面传导模，而且当磁性散射子为长方形、圆形、六角形散射子时产生传导模都不需要晶格畸变，这也是磁性光子晶体异质结所具备的优点. 关键词： 光子晶体 光子带隙结构 传导模     

一维掺杂光子晶体嵌入负介电常数材料和负磁导率材料的性质

对一维掺杂光子晶体嵌入负介电常数材料和负磁导率材料中缺陷模的透射性质进行了研究.利用转移矩阵方法,分别计算了负介电常数材料和负磁导率材料的反射相位谱和一维掺杂光子晶体的透射相位谱.研究发现,在特定条件下,负介电常数材料和负磁导率材料的反射相位以及一维掺杂光子晶体的往返透射相位之和是0或者2π的整数倍.这样的研究结果表明,在满足一定的条件下,一维掺杂的光子晶体嵌入负介电常数材料和负磁导率材料中后,无论杂质的厚度多大,在光子带隙中仅出现一个缺陷模.而且,由于负介电常数材料和负磁导率材料性质的限制,单个缺陷模的品质因子会大大提高.     

石墨点阵柱状光子晶体共振腔的温度特性

构造了一种二维GaAs石墨点阵柱状光子晶体共振腔. 利用时域有限差分方法计算了这种光子晶体共振腔TE_y模的共振峰随温度变化的情况. 计算结果表明这种结构的光子晶体共振腔的共振峰主峰随温度呈分段线性变化趋势,且具有1.60 nm/℃以上的温度响应灵敏度. 同时,计算结果显示,这种结构的光子晶体共振腔具有很好的频率开关特性. 最后,利用计算结果解释了频率开关特性的成因. 关键词： 光子晶体 温度 共振腔 开关     

一维掺杂光子晶体嵌入负介电常数材料和负磁导率材料的性质(英文)

对一维掺杂光子晶体嵌入负介电常数材料和负磁导率材料中缺陷模的透射性质进行了研究.利用转移矩阵方法,分别计算了负介电常数材料和负磁导率材料的反射相位谱和一维掺杂光子晶体的透射相位谱.研究发现,在特定条件下,负介电常数材料和负磁导率材料的反射相位以及一维掺杂光子晶体的往返透射相位之和是0或者2π的整数倍.这样的研究结果表明,在满足一定的条件下,一维掺杂的光子晶体嵌入负介电常数材料和负磁导率材料中后,无论杂质的厚度多大,在光子带隙中仅出现一个缺陷模.而且,由于负介电常数材料和负磁导率材料性质的限制,单个缺陷模的品质因子会大大提高.     

二维棋盘格子复式晶格的完全光子带隙研究

设计了一种棋盘格子复式晶格的二维光子晶体：在二维正方形格子中，把截面为正方形的柱子旋转45°，同时在每个原胞中心引入一个圆形截面的柱子构成的光子晶体结构. 用平面波展开计算棋盘格子复式晶格的完全光子带隙，结果表明：棋盘格子复式晶格的完全光子带隙的Δω/ω比值几乎是普通棋盘格子的5倍，完全光子带隙的个数也增加. 与其他复式结构相比较，发现其最佳的Δω/ω比值是一类粗锐复合结构光子晶体的2.1倍. 关键词： 二维光子晶体 复式晶格 完全光子带隙     

不同晶格光子晶体异质结的界面传导模

利用平面波展开方法与超原胞方法研究了两种不同晶格的光子晶体异质结的界面态. 这两种异质结都是在纯电介质背景上放置空气散射子. 一种异质结由正方形格子上放置正方形散射子和三角形格子上放置六角形散射子组成（SSTH异质结）. 另一种由长方格子上放置长方形散射子和三角形格子上放置圆形散射子组成（RRTC异质结）. 对于SSTH异质结，当沿着界面作晶格的横向拉开或者侧向滑移，都可产生界面态. 而对于RRTC异质结，无需从界面做晶格拉开或者侧向滑移就可产生界面传导模，这个结果有别于其他纯电介质光子晶体异质结的性质. 关键词： 光子晶体 异质结 传导模 超原胞     

多功能磁光子晶体太赫兹可调偏振控制器件

通过对磁场控制下的二维磁光子晶体太赫兹波偏振传输特性的研究,利用铁氧体磁光材料的磁导率随外磁场改变而变化的特点,设计了具有可控起偏、偏振分束和可调谐波片功能的光子晶体太赫兹偏振控制器件.利用平面波展开法和严格耦合波分析分别计算了光子晶体带隙位置和透过率随外磁场强度变化的关系,用时域有限差分法计算了场分布和相位.结果表明,该结构可以实现高偏振消光比的偏振起偏器和分束器,以及在1 THz附近-π-π相位范围的连续可调谐波片. 关键词： 太赫兹 光子晶体 铁氧体 偏振控制     

双周期厚度调制的一维光子晶体的电磁模

计算了厚度调制的双周期一维光子晶体的能带. 当一维光子晶体的厚度被周期性地调制时， 原来的能带分裂为许多子能带，其中一些很窄的子能带进入了原来的单周期光子晶体的带隙 内. 这些窄带内的电磁模的场强具有双周期性分布的特点，并有较强的局域性. 在较宽的子 能带中的电磁模是扩展的. 关键词： 光子晶体 双周期 电磁模     

Modelling of photonic crystals for the design of photonic device based on SOI substrate

In this paper, we report a photonic integrated circuit (PIC), which consisting of a photonic crystal (PC) coupled by a dielectric waveguide to an optical fibre. The PC consists of a sequence of dielectric rods based on a silicon (Si) strip on a silicon dioxide (SiO₂) layer. The finite-difference time-domain (FDTD) method is reviewed and then used to model and predict the optical and the geometrical parameters used to design the fundamental elements of the PIC. The air gap width and the etching depth of the grooves are characterised. The coupling between the PC, and traditional dielectric waveguides is studied and coupling efficiency is evaluated. Diffractive losses are shown to affect strongly the performances of the proposed PIC. In addition, the effect of the air gap width on the diffractive losses and the coupling efficiency between successive neighbouring silicon sections is analysed. The field profile distribution in the structure is calculated and performed. The effects of an incorporated defect are studied, showing a high quality factor.     

基于磁光子晶体的低损耗窄带THz滤波器

本文提出一种采用石榴石型铁氧体磁性材料的太赫兹滤波器,利用波导线缺陷和腔内点缺陷的耦合特性,通过改变腔内介质柱半径及分布,实现对某个波长的耦合,达到了高效率滤波的功能;改变外磁场的大小,影响铁氧体材料的磁导率变化,使谐振频率发生改变,从而对THz波进行滤波.应用平面波展开法(PWM)和时域差分有限法(FDTD)进行仿真分析,研究结果表明,该滤波器其插入损耗为0.0997 d B,3 d B带宽为8.22 GHz,实现了低损耗窄带滤波.     

Localized photonic modes in photonic crystal heterostructures

In this work, interface modes of two-dimensional photonic crystal heterostructures have been investigated by usage of the supercell method. The photonic crystal heterostructure is made of two photonic crystals with square symmetry in which one of them is composed of circular dielectric rods in air background and the other one is constructed by drilled square holes in dielectric. It is shown that using of a proper supercell plays an important role in obtaining the correct interface modes. We have also showed that the guided interface modes and single mode which is different from those reported in some published works are nearly dispersionless.     

Microwave photonic crystal multiplexer and its applications

The application of photonic band gap (PBG) structures to a microwave switch is studied. For this purpose, a frequency selective multiplexer is implemented combining one-dimensional PBG structures. The tunability of microwave photonic crystals (PCs) with ferrites and/or ferroelectric materials is then considered. A theoretical calculation performed on a two-dimensional hexagonal lattice of air rods embedded in a rectangular ferrite slab shows that the PBG is well tunable with external magnetic field parallel to the air rod. We have also discussed the implementation of microwave switch combining the tunability of PBG structures of ferrite and/or ferroelectric materials and the frequency selective nature of PBG multiplexer.     

Band gap studies of 2D photonic crystals with hybrid scatterers

Two-dimensional (2D) photonic crystals (PCs) of a square lattice with dielectric hybrid rods in air are proposed; these PCs consist of a square rod at the center of the unit cell and additional circular rods with their outermost edges against the middle of each side of the lattice unit cell. The band gap structures of PCs can be tailored and optimized by rotating the square rods and adding circular rods to the lattice unit cell. The variation of bands near the complete photonic band gap boundaries, due to some specific modes, is sensitive to certain structural parameters of the system. The results can be understood by analyzing the spatial energy distribution of the electromagnetic fields. Based on such a field analysis, a novel interpretative model is proposed. The PC can be fabricated easily and operated in the microwave region and, hence, should be suitable for applications in new microwave devices.     

Asymmetric light transport in L-shaped and U-shaped photonic crystal waveguides

We present an asymmetric light transport in a modified U-shaped photonic crystal waveguide (PCW). The compact waveguides consist of coupling two L-waveguides in a PC formed by dielectric rods in air arranged in a square lattice. We show that the transmitted power flow depends on the direction of the incident light, the transmission varies between a high and low value upon switching the position of the source beam from the input to the output of the PCW. Computations are performed using the plane wave expansion and finite-difference time-domain methods.     

Magneto-phonon polaritons in two-dimension antiferromagnetic/ion-crystalic photonic crystals

Magneto-phonon polaritons in a two-dimension photonic crystal (PC) are discussed. This PC is constructed by embedding a periodical square lattice of ionic-crystal cylinders into an antiferromagnet. The two media are dispersive, with their individual resonant frequencies near each other. We first set up an effective-medium method to obtain the effective magnetic permeability and dielectric permittivity of the PC, followed by the dispersion relations of surface and bulk polaritons. There are a number of new surface polaritons, and two new distinctive bulk polariton bands in which the negative refraction and left-handedness can appear. The numerical calculations are based on the example, FeF₂/TlBr PC.     

外磁场与温度对低温超导光子晶体低频禁带特性的影响

文中用传输矩阵法(TMM)分析了TM波垂直入时,超导光子晶体的低频禁带特性,并讨论了外磁场与温度对禁带的影响.分析结果表明:超导光子晶体存在频率从0开始的低频禁带;当没有外磁场作用时,由于超导中正常态电子的影响,低频禁带的截止频率与温度无关;有外磁场作用时,温度才对截止频率具有可调性.外加恒定磁场时,低频禁带的截止频率随温度升高而减小;而在正常态电子的作用下,温度对处在超导态超导光子晶体禁带截止频率的调节范围相对忽略正常态电子情况下减小.恒温下,通过调节外磁场来控制带隙时,正常态电子的贡献很小可忽略不计;外磁场强度增大禁带截止频率减小.当超导体完全处于正常态时,低频禁带消失.     

Photonic band gaps in two-dimensional photonic crystals of core-shell-type dielectric nanorod heterostructures

A new type of two-dimensional photonic crystal (PC) called core-shell-type PC composed of a nanorod heterostructure array in a square or triangular lattice such that a dielectric nanorod is covered by a thin interfacial layer is studied. Using the plane-wave numerical expansion method, we study the modification of the band gap spectrum when the nanorods are covered by other material, and reveal that the photonic band gap is considerably enhanced in size for both square and triangular lattice. The effects of structural parameters on the band gaps are also studied. The results show that there exist optimal parameters to open large gaps, and TE (Transverse-electric) band gaps are favored in a triangular lattice.     

二维函数光子晶体

光子晶体是由两种或两种以上不同介电常数材料所构成的周期性光学纳米结构.光子晶体结构可分为一维、二维和三维,其中二维光子晶体已成为研究的热点.可调带隙的二维光子晶体可以设计出新型的光学器件,因此,对它的研究具有重要的理论意义和应用价值.本文提出的二维新型函数光子晶体可以实现光子晶体带隙的可调性.所谓二维函数光子晶体,即组成它的介质柱的介电常数是空间坐标的函数,它不同于介电常数为常数的二维常规光子晶体.二维函数光子晶体是通过光折变非线性光学效应或电光效应使介质柱的介电常数成为空间坐标的函数.运用平面波展开法给出了TE和TM波的本征方程,由傅里叶变换得到二维函数光子晶体介电常数ε(r)的傅里叶变换ε(G),其傅里叶变换比常规二维光子晶体的复杂.计算发现当介质柱介电常数为常数时,其傅里叶变换与常规二维光子晶体的相同,因此二维常规光子晶体是二维函数光子晶体的特例.在此基础上具体研究了二维函数光子晶体TE波和TM波的带隙结构,其介质柱介电常数函数形式取为ε(r)=k·r+b,其中k,b为可调的参数.并与二维常规光子晶体TE波和TM波的带隙结构进行了比较,发现二维函数光子晶体与二维常规光子晶体TE波和TM波的带隙结构有明显的区别,二维函数光子晶体的带隙数目、位置以及宽度随参数k的变化而发生改变.从而实现了二维函数光子晶体带隙结构的可调性,为基于二维光子晶体的光学器件的设计提供了新的设计方法和重要的理论依据.