基于太极形介质柱六角光子晶体禁带特性研究

提出了一种新型的非对称性散射体的二维六角晶格光子晶体结构–-太极形介质柱光子晶体. 利用平面波展开法从理论研究这种光子晶体结构的能带特性以及结构参数对完全禁带的影响. 研究表明:散射体对称性的打破, TE模和TM模能带宽度和数目都会有所增加, 有益于获得更宽的完全禁带以及更多条完全禁带.通过参数优化, 发现在ε = 17, R=0.38 μm, r=0.36R, θ = 0° 时, 获得最大完全带隙宽度0.0541(ωa/2πc); 在ε = 16, R=0.44, r=0.2R, θ = 0°时, 光子晶体完全带隙数目最多达到8条. 关键词： 光子晶体 禁带 平面波展开     

大带隙二维三角格子光子晶体结构参数的优化设计

光子晶体结构设计优化是理论研究的一个重要内容.运用平面波展开法对圆柱、方柱及正六边柱构造的二维三角格子光子晶体的禁带进行仿真计算,讨论了介质材料分别为GaAs、Si和Ge情况下,柱子形状、旋转角度、填充比的变化对完全光子禁带的影响.发现:对于二维三角格子光子晶体,相对于介质柱,空气柱更易获得完全光子禁带;而相对于圆柱及...     

The effect of etching interfacial layers on the absolute photonic band gap in two-dimensional photonic crystals

The photonic band structures of two-dimensional (2D) photonic crystals with etched interfacial layers between air rods and the background dielectric is studied theoretically. The effect of etching interfacial layers on absolute photonic band gap (PBG) is analyzed quantitatively. Numerical calculations are carried out based on Maxwell's equations and the plane-wave expansion method. It is shown that the physical property of interfacial layers influence the absolute PBG, and the existence of interfacial layers cannot enlarge the largest absolute PBG of an ideal case without interfacial layers.     

Huge photonic band gaps with strong attenuations resulted from quasi-one-dimensional waveguide networks composed of triangular fundamental loops

In order to design systems generating large photonic band gaps (PBGs), in this paper we construct interesting quasi-one-dimensional (quasi-1D) periodic triangular, diamond, and tetrahedral networks composed of 1D waveguides and triangular fundamental loops. The optical frequency band structures and photonic attenuation behaviors of electromagnetic (EM) waves propagating in the three kinds of one- and two-segment-connected (1SC and 2SC) networks without dissipation are, respectively, investigated and we find that huge PBGs can be produced in the middle of a frequency period and the widths of the largest PBGs can be controlled by adjusting the matching ratio of waveguide length. When the ratio equals 2:1, the width of the hugest PBG resulted in tetrahedral network reaches 0.73 times of a frequency period and is about 1.16 times of the best result reported previously. The average attenuations of the largest PBGs are very strong and increase rapidly with the increment of the number of unit cell. This makes our designed networks with very few unit cells exhibit wonderful PBG features and they can be realized in experiments easily. It may be useful for the designing of optical devices with large PBG and strong attenuation.     

Comparison of photonic bandgaps of two-dimensional periodic and quasi-periodic photonic crystals with different relative permittivity dielectric

Photonic bandgaps (PBGs) of two-dimensional (2D) triangular-lattice and square-lattice and decagonal quasi-periodic photonic crystals (PCs) have been analyzed, with a given scatterer radius and dielectric relative permittivity changing from 1 to 30 within air-cylinders-in-dielectric and dielectric-cylinders-in-air constructions. The results have shown that 2D quasi-periodic PC is more likely to generate PBG and complete PBG than 2D periodic PC. For the given scatterer radius and two constructions, PBG widths of the two types of 2D PCs vary little, whereas the corresponding center frequencies decrease in smooth “hyperbola-like” curves with dielectric relative permittivity increasing monotonically. The present results will guide the design of PBG-type microstructure photonic devices.     

Larger absolute photonic band gap in two-dimensional air–silicon structures

We investigate different aspects of the absolute photonic band gap (PBG) formation for two-dimensional photonic crystals, consisting of air rods drilled into silicon. Specifically, square lattices of square and circular rods are considered. The lattice symmetry, shape and orientation of the rods affect the photonic gap parameters. A symmetry reduction by addition of a smaller different shaped rod into the center of the lattice unit cell can produce significantly larger band gap. Combining the symmetry reduction and rotation of the noncircular rods yields the greatest improvements in the size of absolute band gap. We discuss the maximization of the absolute PBG width as a function of lattice parameters and the practical fabrication feasibility of these optimized structures.     

Complete photonic band gaps in one-dimensional ternary photonic crystals containing single negative materials

Complete photonic band gaps (PBGs) are found in one-dimensional ternary photonic crystals (1D TPCs) composed of an ordinary dielectric and single negative metamaterials. The proposed TPC gives omni directional PBG completely independent of polarizations dependent weekly on angle of incidence. Here the choice of different parameters of TPC is done in such a way so that it eliminates the Brewster's-angle transmission resonance, thus allowing a complete 3D PBG. It exhibits a photonic band or gap near frequencies where either the magnetic permeability or the electric permittivity of the metamaterial changes sign, whose width increases with the increasing angle of incidence. These result from the dispersive properties of the metamaterials and disappear for the particular case of propagation along the stratification direction. The results are discussed in terms of incident angle, layer thickness, dielectric constant of the dielectric material for TE and TM polarizations.     

Magnetic surface plasmon-induced tunable photonic bandgaps in two-dimensional magnetic photonic crystals

We experimentally studied magnetically controllable photonic band gaps (PBGs) in two-dimensional magnetic photonic crystals consisting of ferrite rods. Besides the conventional PBG that relates to Bragg scattering, two other types of PBG, resulting from magnetic surface plasmon (MSP) resonance and spin-wave resonance, respectively, are observed. The PBG due to MSP resonance is particularly interesting because of its analogy to surface plasmon in metal; furthermore, it is shown to be completely tunable by an external static magnetic field from both an experimental and a theoretical point of view.     

电磁波在周期介质中的传播及二维光子晶体的光子带结构

光子晶体是光学与凝聚态物理交叉的新领域,也是近年来应用物理学的一个重要研究领域,它是一种由介电常数高的(低的)介质在另一种介电常数低的(高的)背景介质中周期排列所组成的人造多维周期结构材料,能够产生光子带隙。频率落在带隙内的光在晶体里沿任何方向都不能传播,因而具有能够抑制原子、分子的自发辐射等诱人的光电子学特性,在基础研究和实际应用上都有着巨大的潜力。本文在这一领域里进行了富有成效的研究,获得了很好的结果。主要有:(1)利用平面波展开方法来计算二维光子晶体的带隙结构。首先,我们设计正方晶胞的二维光子晶体模型。设x₃方向为介质柱的轴方向,二维周期结构在x₁-x₂平面上。晶胞的晶格常数为a,半径为r,介质柱和空气柱的介电常数分别为ε_a=17和ε_b=1,a>2r。设计的核心思想是通过降低光子晶体结构的对称性,消除光子能带在晶体的布里渊区高对称点上的本征简并。(2)对于二维光子晶体的电磁波理论及周期介质中的Bloch波解做了详细的推导,给出了光子晶体中禁带存在的理论依据。同时以正方格子晶格的二维光子晶体为例,验证了电介质在空气圆孔中的排列存在E偏振和H偏振的光子带隙重叠区,称为绝对光子带隙。对于二维的光子晶体,两种本征偏振模式的光子能带结构可以独立地调节,以实现两者的光子带隙的最优重叠, 从而大大提高了二维光子晶体的完全带隙宽度。     

Large photonic band gaps and strong attenuations of two-segment-connected Peano derivative networks

In this Letter, based on ancient Peano curves we construct four kinds of interesting Peano derivative networks composed of one-dimensional (1D) waveguides and investigate the optical transmission spectra and photonic attenuation behavior of electromagnetic (EM) waves in one- and two-segment-connected networks. It is found that for some two-segment-connected networks large photonic band gaps (PBGs) can be created and the widths of large PBGs can be controlled by adjusting the matching ratio of waveguide length and are insensitive to generation number. Diamond- and hexagon-Peano networks are good selectable structures for the designing of optical devices with large PBG(s) and strong attenuation(s).     

空气环型二维光子晶体完全带隙特性研究

采用平面波展开法, 系统研究了空气环型二维光子晶体的完全光子带隙随结构参数变化而改变的规律, 并将其与普通的空气孔型和介质柱型二维光子晶体的完全带隙进行了比较. 研究表明: 空气环型二维光子晶体不仅可以获得更宽的完全带隙, 而且, 当介质折射率较低时, 其可以获得普通空气孔型和介质柱型二维光子晶体在低折射率条件下所无法获得的完全带隙. 关键词： 空气环型二维光子晶体 完全带隙 平面波展开法     

Tunable photonic band-gaps in one-dimensional photonic crystals containing linear graded index material

We have demonstrated control of the photonic band gaps (PBGs) in 1-D photonic crystals using linear graded index material. The analysis of PBG has been done in THz region by considering photonic crystals in the form of ten periods of second, third and fourth generation of the Fibonacci sequence as unit cell. The unit cells are constituted of two kinds of layers; one is taken of linear graded index material and other of normal dielectric material. For this investigation, we used a theoretical model based on transfer matrix method. We have obtained a large number of PBGs and their bandwidths can be tuned by changing the grading profile and thicknesses of linear graded index layers. The number of PBGs increases with increase in the thicknesses of layers and their bandwidths can be controlled by the contrast of initial and final refractive index of the graded layers. In this way, we provide more design freedom for photonic devices such as reflectors, filters, optical sensors, couplers, etc.     

Study on the anisotropic photonic band gaps in three-dimensional tunable photonic crystals containing the epsilon-negative materials and uniaxial materials

In this paper, the properties of anisotropic photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) composed of the anisotropic positive-index materials (the uniaxial materials) and the epsilon-negative (ENG) materials with body-centered-cubic (bcc) lattices are theoretically studied by a modified plane wave expansion (PWE) method, which are the uniaxial materials spheres inserted in the epsilon-negative materials background. The anisotropic photonic band gaps (PBGs) and one flatbands region can be achieved in first irreducible Brillouin zone. The influences of the ordinary-refractive index, extraordinary-refractive index, filling factor, the electronic plasma frequency, the dielectric constant of ENG materials and the damping factor on the properties of anisotropic PBGs for such 3D PCs are studied in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in such 3D PCs with bcc lattices composed of the ENG materials and uniaxial materials, and the complete PBGs can be obtained compared to the conventional 3D PCs containing the isotropic materials. The calculated results also show that the anisotropic PBGs can be manipulated by the parameters as mentioned above except for the damping factor. Introducing the uniaxial materials into 3D PCs containing the ENG materials can obtain the larger complete PBGs as such 3D PCs with high symmetry, and also provides a way to design the tunable devices.     

Theoretical predictions of photonic properties of nanoporous copolymer films as photonic band gap materials using FDTD

Block copolymers (BCPs), which self-organize into ordered 1-, 2- and 3-dimensional periodic equilibrium structures, can exhibit photonic band gaps (PBGs). In this paper, cylinder microdomain nanoporous films are proposed to be treated as a new kind of 2-dimensional BCP based photonic crystal. The minor component of the nanoporous films has been removed chemically with only pores left in order to enhance their dielectric constant contrast, which provides a new solution to achieve necessary PBG properties with BCPs. The finite-difference time-domain (FDTD) method is used to investigate band features of this kind of photonic crystal theoretically. It is noted that the complete band gaps for the H polarization are obtained, although for the E polarization only the incomplete gaps exist. In addition, the gap map of the PBG materials is presented and its characteristics are analyzed. PACS 42.70.Qs; 42.70.Jk; 42.25.Bs     

Intersecting veins effects of a two-dimensional photonic crystal with a large two-dimensional complete bandgap

Optimal design of a two-dimensional photonic crystal with a square lattice of dielectric rods with intersecting veins in GaAs is investigated numerically using plane wave expansion method. It is shown how a maximum complete two-dimensional bandgap is obtained by optimally connecting the dielectric rods with intersecting veins. The complete two-dimensional photonic bandgap (PBG) of our optimal design reaches Δω = 0.10664(2πc/a) (where a is the lattice constant and c is the speed of light in vacuum) when the radius of dielectric rod is 280.1 nm and the half-vein width is 60 nm. Our result shows 40% the width of PBG higher than that obtained from Ref. [M. Qiu, S. He, J. Opt. Soc. Am. B 17 (2000) 1027] (Δω = 0.0762(2πc/a)). In addition, we found that the complete bandgap can be obtained in a large range of radius R of dielectric rod when the half width of intersecting veins d is larger than 65 nm.     

Defect and dope selective of transmission properties of 2D photonic crystal

The effects of the defect and doping on the transmission properties are investigated in two-dimensional photonic crystal (PC) with triangular rods using the finite difference time domain (FDTD) method. The results show that the width and the central position of the photonic band gap (PBG) depend on the thickness of rods with defect or composite-defect, and the refractive index of doped dielectric rods. The transmission properties of composite-defect combined with doping are further investigated. The thinner the nested concentric triangular rod and the smaller the refractive index is, the wider the band gaps is.     

Study on complete band gap of two-dimensional photonic crystal with quadrangular rods

The plane wave expansion method (PWM) was employed to study the relation between the photonic band gap (PBG) of 2D triangular lattice photonic crystal (PC) and the shapes of rods and dielectric constant. It is shown that the PBG of PC with quadrangular rods is the widest one, compared with the other case with cross section shapes of triangular, circular and hexagon under the same filling ratio, and a peak value appears when the side length ratio of l_x/l_y is equal to 1.21 approximately to any filling ratio. In the aspect of the effects of dielectric constant, the PBG width does not increase monotonically with the increase permittivity ?₂ of the background material to certain permittivity ?₁ of the quadrangular rods, but has a peak value instead. However, the larger the permittivity ?₁ is, the narrower the band width is and the lower the central frequency is, and the dispersion Δ? = ?₂ − ?₁ is larger also.     

受限原子蒸气/电介质周期层状结构中光子带隙的厚度调制

周期性受限原子蒸气/电介质层光子带隙（PBG）宽度及其诱导的反射平顶随蒸气层厚度 d的增大而变宽,并在 （ 为原子的共振波长)时达到最大值,之后随d的增大呈变窄趋势. 随着蒸气厚度的增大,带隙的中心频率产生红移,厚度越大,红移量越大. 研究还发现,共振波长处的反射及透射谱具有迪克窄化结构. 这种可调谐的PBGs结构可望用于全光反射镜及滤波器.     

受限原子蒸气/电介质周期层状结构中光子带隙的厚度调制

周期性受限原子蒸气/电介质层光子带隙(PBG)宽度及其诱导的反射平顶随蒸气层厚度d的增大而变宽,并在d/(λ0/2)=0.5(λ0为原子的共振波长)时达到最大值,之后随d的增大呈变窄趋势.随着蒸气厚度的增大,带隙的中心频率产生红移,厚度越大,红移量越大.研究还发现,共振波长处的反射及透射谱具有迪克窄化结构.这种可调谐的PBGs结构可望用于全光反射镜及滤波器.     

Photonic amorphous diamond structure with a 3D photonic band gap

We report that a full three-dimensional (3D) photonic band gap (PBG) is formed in a photonic amorphous structure in spite of complete lack of lattice periodicity. It is numerically shown that the structure "photonic amorphous diamond" possesses a sizable 3D PBG (18% of the center frequency for Si-air dielectric contrast) and that it can confine light at a defect as strongly as conventional photonic crystals can. These findings present important new insight into the origin of 3D PBG formation and open new possibilities in developing 3D PBG materials.