二维正方柱结构光子晶体禁带的研究

利用平面波展开法通过计算机模拟仿真对二维正方排列介质方柱和空气方柱结构以及三角排列介质方柱和空气方柱结构进行了禁带研究。研究发现：这四种二维光子晶体结构都存在完全禁带。介质方柱结构具有较大的TM禁带,而空气方柱结构具有较大的TE禁带。当介质方柱宽度增大时,禁带中心频率均向低频移动,而当空气方柱宽度增加时,禁带中心频率均向高频移动。当增大材料折射率时,禁带中心频率均向低频移动。对于空气方柱结构,应该选取高折射率材料,以提高完全禁带的带隙率。     

大带隙2维正方晶格光子晶体的优化设计

为了研究2维正方晶格光子晶体的完全带隙特性,采用平面波展开方法模拟了两种结构2维光子晶体,在固定光子晶体周期常数a的前提下,研究了2维正方晶格光子晶体的完全禁带随柱半径和折射率的变化规律。结果表明,以空气为背景的锗介质柱组成的光子晶体,随着半径的增大,完全带隙宽度先增大后减小最后消失,填充比为38.3%时,同时增大介质柱的介电常数,在介质柱折射率为4.2处,完全带隙最大,带宽是0.02754(ωa/(2πc));以锗为背景的空气柱组成的光子晶体,光子禁带对应的无量纲频率随半径的增大而增大,填充比为48.3%时,同时增大背景介质的介电常数,出现多个完全带隙,在背景折射率为6.2处,完全禁带最大,带宽为0.02922(ωa/(2πc))。光子晶体带隙的频谱响应也表明了完全带隙的范围。这为大带隙2维正方晶格光子晶体的设计和制备提供了依据。     

二维介质圆柱型光子晶体完全禁带与结构参数的关系

利用Bandsolve软件分别优化计算得到GaAs、Si、Ge三种材料的二维介质圆柱型光子晶体完全禁带与晶格结构、填充比、介电常数比三个主要影响因素之间的关系。研究发现,当填充比(r／a)介于0．1～0．5时,对于六边形晶格,三种材料都不存在完全禁带;四边形晶格,Ge存在较窄的完全禁带,GaAs和Si不存在完全禁带。对于蜂窝形晶格,当填充比介于0．18～0．5时,三种材料均存在较大的完全禁带,而且,介电常数比越大,完全禁带宽度越大。所得结果对二维介质圆柱型光子晶体的制作和进一步应用研究奠定了理论依据。     

二维Kagome格子光子晶体禁带的数值模拟

采用平面波展开法模拟计算了由空气背景中的介质柱构成的二维Kagome格子光子晶体的能带结构，得到了使完全光子禁带最大化的结构参量．计算结果表明：由圆形、正六边形和正四边形三种不同形状锗介质柱构成的Kagome格子光子晶体都出现了完全光子禁带，最大禁带分别为△=0．014(ωa／2πc)、△=0．013(ωa／2πc)、△=0．011(ωa／2πc)．发现由圆形和正六边形两种介质柱构成的Kagome格子光子晶体在填充比连续变化的较大的范围内都有宽度较为稳定的完全禁带，且它们具有非常相似的能带结构．     

2维超晶格结构光子晶体传输特性研究

为了研究超晶格结构对光子晶体禁带的影响,应用时域有限差分法对圆/椭圆、圆/复合柱超晶格结构光子晶体的传输特性进行了计算,得到了相应的透射谱.结果表明,对圆/椭圆超晶格,禁带宽度随椭圆柱截面积的增大而变宽,中心频率变大;对于圆/复合柱超晶格结构,椭圆柱内接于圆孔时,禁带宽度随截面积的增大而变窄,中心频率变小;当长轴垂直入射波方向时,高频段出现较宽禁带,低频禁带完全消失;而椭圆孔中内嵌圆柱时,禁带宽度变化与前者相反.该研究为光子晶体器件的制作提供了理论依据.     

太赫兹波在金属光子晶体中的传播特性

构造了一种适用于太赫兹器件的二维金属光子晶体结构。研究了晶格常数α=0. 3mm的正方晶格二维铜介质柱光子晶体,这样的结构在工艺上相对容易实现。在0 ~2THz频段范围内,发现当金属柱半径从0. 1α到0. 3α变化时,随着圆柱半径的增大,禁带的中心频率上移,并且带隙的宽度增大;当金属柱半径为0. 32α时,出现了两个禁带。研究结果为性能优良的THz器件开发提供了理论依据。     

复式晶格光子晶体光纤带隙分析

提出了一种复武晶格光子晶体光纤,通过向传统正方形格子空气孔光子晶体光纤中引入半径相同但折射率为负的介质柱,构成两种正负折射率介质柱嵌套的周期性排列结构.用平面波法分析这种光纤的光子带隙,仿真结果表明:与传统的正方形格子空气孔光子晶体光纤相比,当R/A=0.35,衬底折射率nb=1.30,空气孔折射率na=1.0,介质柱折射率nc=-1.0时,这种光纤可以实现光子带隙效应导光;当品格常数A的范围为1.5～3.0μm时,传输波长范围为880～2 300 nm.     

完全禁带二维光子晶体的研究

利用平面波展开法,对存在完全禁带的正三角排列的气柱型二维光子晶体和蜂窝状排列的介质柱型二维光子晶体进行了研究,分析了柱的半径和介质折射率对完全禁带大小的影响,结果表明,正三角排列气柱型比蜂窝状排列介质柱型具有更大的最大带隙率,而且最大带隙率还可以通过介质折射率的改变来优化;蜂窝状排列介质柱型二维光子晶体最容易加工的结构刚好适合常见材料硅或砷化镓,具有更大的实用价值.     

一种新型光子晶体环形腔THz波滤波器

文章提出一种新型光子晶体环形腔THz波滤波器,在该滤波器的光子晶体环形腔内部引入一个正方形介质柱,四周各引入一个散射介质柱,基底材料采用折射率n=3.4的硅,晶格常数A为30μm。应用基于FDTD(时域有限差分法)的Rsoft软件进行仿真分析,结果表明,当介质柱半径为5.157 5μm,内部正方形介质柱边长为92μm且其旋转角为6°,散射介质柱半径为5μm时,94.053μm波长的透射率为0.985 56。     

基于厚度精确法用遗传算法搜索一维宽带隙光子晶体

本文用遗传算法设计了大禁带的一维光子晶体.用传输矩阵法计算光子晶体能带.光子晶体的初始结构由计算机随机产生,通过遗传算法对光子晶体结构进行了优化,得到最大全方位相对禁带宽度(定义为禁带宽度与禁带中心之比)的一维光子晶体.发现由多种介质材料构建多层的一维光子晶体原胞时,折射率最大和最小的两种材料构成的两层结构的光子晶体相对禁带宽度最大,而且一维两层结构光子晶体的全方位禁带宽度随着两种介质折射率差的增大而增大,最后会达到一个饱和值200%.并研究了TM、TE模式的相对禁带宽度与光入射角的关系.     

Off-plane angle dependence of photonic band gap in atwo-dimensional photonic crystal

We present an analysis of off-plane angle dependence of the photonic band gap in a two-dimensional triangular lattice with circular air rods embedded in a dielectric background. The plane-wave expansion theory is used to calculate band structures within the first Brillouin zone, and an effective refractive index approach is introduced to derive the off-plane angle dependence. The off-plane angle at which the in-plane band gap decreases to half of its gap width has been obtained, which can be increased significantly by increasing the filling fraction of the air rods. For a typical semiconductor material with a refractive index of 3.6 as the background, this angle reaches 26° at a high filling fraction of 0.84 (where the normalized in-plane band gap width is 24%). The corresponding solid angle of 1.75π could cover about 60 of the spontaneous emission from a linear-polarized dipole along the air rods     

Numerical simulation of absolute photonic band gaps for two-dimensional photonic crystals with the rotational square lattice

The band gap of two-dimensional (2D) photonic crystals with the square lattice of rotational square air columns made of GaAs and Ge is analyzed by the plane wave expansion method. The effects of dielectric refractive index and crystal structures on the absolute photonic band gap are investigated. The results show that the maximum absolute photonic band gap emerges when the square air columns are rotated for 30° and the filling ratio f of the medium is 0.3276. It is also noticed that absolute photonic band gaps appear when the refractive index of the medium (n) is 2.61. When n=3.70, the width of the absolute photonic bandgaps reaches the maximum.     

Suppression of spontaneous emission for a two-dimensional honeycombphotonic bandgap structure estimated using a new effective-index model

The suppression of spontaneous emission introduced by a two-dimensional honeycomb-rod photonic bandgap structure is evaluated using the plane-wave expansion theory. An analysis of the out-of-plane angle dependency on the photonic bandgaps through the application of a new effective refractive-index model is presented. The in-plane properties for structures characterized by a rod dielectric constant in the range from 1.0 to 15.0, air background, and a filling fraction in the range from 0.07 to 0.4 are analyzed, and a structure with a relative in-plane bandgap of 10% is chosen. The out-of-plane angle analysis is performed for this structure, and it is found that propagation for modes within a narrow frequency interval is inhibited for a solid angle of 2.16 π, covering 54% of the spontaneous emission from a narrow-linewidth point source     

Theoretical optimization of complete forbidden bands in woodpile-type photonic crystals

Based on the plane-wave method, the optical properties of complete forbidden bands of woodpile structure photonic crystal with an entire Lattice rotation of 45° in the x-y plane were theoretically studied in terms of height-to-pitch ratios, filling factors, and rotation angles. The calculated results show that the gap to mid-gap ratio changes slightly with a filling fraction ranging from 0.25 to 0.30. The optimum height-to-pitch ratio is about 1.3. The gap to mid-gap ratio reaches more than 0.18 when the rotation angle increases from 40° to 50° and the maximum gap to mid-gap ratio of 0.2 remains unchanged for the rotation angle from 42°to 48° with a constant height-to-pitch ratio of 1.3. The gap to mid-gap ratio reaches the maximum value of 0.2 when the height-to-pitch ratio is 1.3. This woodpile-type photonic crystal can provide large band gaps within a wider parameter range, which makes it convenient to manufacture three-dimensional photonic crystals in the laboratory.     

四方格子全固光子带隙光纤带隙特性研究

基于平面波展开法,对四方格子全固光子带隙光纤带隙随结构的变化特性进行了数值模拟,并与具有相同结构参数三角格子全固光子带隙光纤进行了比较,数值结果表明带隙的位置由高折射率棒的结构参数决定,而与高折射率棒的排列方式和棒之间的间距无关,这一结果与反谐振效应非常吻合。最后对理想和实际拉制出的四方格子的全固态光子带隙光纤的带隙进行了比较,得出了在设计光纤时,应利用较低的带隙的结论。     

Bandgap analysis of 2D photonic crystals with Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method

In this paper, an accurate and rapid method is presented to characterize bandgaps of photonic crystals (PCs) constituted by two-dimensional (2D) arrays of dielectric rods with rectangular and circular cross sections. The transmittance and reflectance spectrums of finitely periodic 2D PCs are analyzed using the combination of Rigorous Coupled Wave Analysis (RCWA) and Generalized Scattering Matrix (GSM) methods. In the proposed method, band-edge frequencies of infinitely periodic 2D PCs are determined via Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method using RCWA as a sub-block code. Numerical investigations show that estimating the band-edge frequencies of ideal 2D PCs via AFGSM method is identical with determining the bandgaps of the finite periodic global structure. The high convergence rate of the proposed technique also allows us to perform a bandgap characterization including the higher order Floquet modes without solving the eigenvalue equations for each cascaded layer. Furthermore, the variation of bandgaps when modifying the incidence angle, physical and geometrical parameters are presented for both TE and TM polarizations. The effect of introducing defect in 2D PC structure and resulting band natures are outlined. Our results are in excellent agreement with both theoretical and experimental results in the literature.     

光子晶体与光子准晶复合型上下载滤波器

基于二维正方晶格光子晶体与十二重Stamfli型光子准晶提出了单环形腔上下载滤波器及双环形腔串联上下载滤波器.分析并对比了两种上下载滤波器的传输效率随光子准晶介质柱半径及折射率大小的变化规律,且对比了两种上下载滤波器的品质因数随环形腔中心介质柱半径及折射率大小的变化规律.结果表明,双环形腔串联复合型上下载滤波器的性能优于单环形腔复合型上下载滤波器.研究结果将为设计及制备优良上下载滤波器件提供一定指导作用.