Photonic band gap engineering in 2D photonic crystals

The polarization-dependent photonic band gaps (TM and TE polarizations) in two-dimensional photonic crystals with square lattices composed of air holes in dielectric and vice versa i.e., dielectric rods in air, using the plane-wave expansion method are investigated. We then study, how the photonic band gap size is affected by the changing ellipticity of the constituent air holes/dielectric rods. It is observed that the size of the photonic band gap changes with changing ellipticity of the constituent air holes/dielectric rods. Further, it is reported, how the photonic band gap size is affected by the change in the orientation of the constituent elliptical air holes/dielectric rods in 2D photonic crystals.     

Tuning of full band gap in anisotropic photonic crystal slabs using a liquid crystal

We analyze the tunability of full band gap in photonic crystal slabs created by square and triangular lattices of air holes in anisotropic tellurium background, considering that the regions above and below the slab are occupied by SiO₂ and the holes are infiltrated with liquid crystals. Using the supercell method based on plane wave expansion, we study the variation of full band gap by changing the optical axis orientation of liquid crystal. Our results demonstrate the existence and remarkable tunability of full band gap in both square and triangular lattices, largest band gap and tunability being obtained for the triangular lattice.     

Control of photonic band gaps in one-dimensional photonic crystals

The photonic band gaps in one-dimensional photonic crystals (PCs) are theoretically investigated. A new method to broaden the photonic band gaps is introduced. Based on the similar method, a kind of photonic crystals is constructed to generate photonic band gaps with proportioned central frequencies. This technology can be used for designing nonlinear PCs for harmonic generation.     

Effect of anisotropy on the photonic band gap and surface polaritons of a one-dimensional single-negative photonic crystal

The effect of anisotropy on the photonic band structure and surface polaritons of a one-dimensional photonic crystal made of uniaxially anisotropic epsilon-negative (ε<0,μ>0) and mu-negative (ε>0,μ<0) metamaterials is theoretically investigated. Two different cases of uniaxially anisotropic epsilon-negative and mu-negative metamaterials are considered. It is found out that for one case of anisotropy, one-dimensional photonic crystal does not have any single-negative band gap. As a result, it can not support the surface polaritons. While, for another case, the structure shows single-negative band gaps. So, the surface polaritons can be excited at the interface of such a photonic crystal. However, these surface polaritons, unlike the isotropic case, are not omnidirectional and they are restricted to a limited rang of the propagation constant.     

中红外波段硅基两维光子晶体的光子带隙

利用电化学腐蚀的方法制备了大多孔硅两维光子晶体.结构图形对称性为正方格子，其结构参数为正方形晶格周期a=44μm，正方形空气柱的边长l=2μm.并用显微红外光谱仪表征了光谱性质，揭示了所制备两维光子晶体样品的中红外波段光子的反射特性. 关键词： 光子晶体 光子带隙 反射谱 时域有限差分法     

Eye-protection glasses against YAG laser injury based on the band gap reflection of one-dimensional photonic crystal

Eye-protection glasses against YAG laser injury based on band gap reflection of one-dimensional photonic crystal (PC) is designed and manufactured in this paper. The laser beam (wavelength 1.06 μm) is reflected by the one-dimensional PC (with the transmission 10⁻⁷) and absorbed by the phosphatic glass substrate (with the transmission 1% for 1.06 μm), so the transmission of the device for wavelengths of1.06 μm can reach 10⁻⁹. The glasses have enough capabilities to protect the eyes from injury of ns-YAG lasers whose energy density is 1 J/cm² for all incident angles, and also to avoid a second injury to others from the reflected laser beams. The transmission of the glasses is beyond 70% for the visible lights. The testing data of the eye-protection glasses agree well with the theoretical predictions.     

Numerical analysis of a temperature sensor based on the photonic band gap effect in a photonic crystal fiber

In this paper we investigate, by the plane wave expansion method and an analytical model, the temperature effect on the photonic band gap fiber, and we report on a numerical demonstration of a temperature sensor based on the photonic band gap (PBG) shift in a solid core photonic crystal fiber (PCF) infiltrated with a high refractive index oil. The bandwidth and the position of the central wavelength of the band gap are the parameters of interests for our temperature sensing purpose. Simulation results were found to be in excellent agreement with the refractive index scaling law and the highest sensitivity of 3.21?nm/°C was achieved, and it will be even higher than the grating based sensors written in PCFs with similar structure.     

Zero permittivity band characteristics in one-dimensional plasma dielectric photonic crystal

We consider the oblique propagation of electromagnetic waves in one-dimensional plasma dielectric photonic crystals, the superlattice structure consisting of alternating plasma and dielectric materials using transfer matrix method. Our results show that photonic band gaps for all polarizations can be obtained in one-dimensional plasma dielectric photonic crystals. These structures can exhibit a new type of band or gap, for the incidence angles other than normal incidence, near frequencies where the electric permittivity of the plasma layer changes sign. This new band or gap arises, from the dispersive properties of the plasma layer, only for TM polarized waves and its width increases with the increasing angle of incidence. This differential behaviour under polarization can be utilized in the design of an efficient polarization splitter. The band characteristic is affected by the plasma width, the plasma density, dielectric width, the dielectric constant of the dielectric medium and angle of incidence.     

含有理想导体的准分形结构光子晶体的能带

用时域有限差分方法计算了一组具有相似几何结构且包含理想金属材料的准分形光子晶体的能带.数值计算结果表明，这种准分形结构光子晶体具有绝对带隙，且带隙的宽度会 随着分形级数的增大而增大.同时，随着级数的增大，其能带在整体地趋向于高频端的同时，能带会被快速拉直而形成孤立的能级. 关键词： 光子晶体 带隙 分形     

Enlargement of absolute photonic band gap in modified 2D anisotropic annular photonic crystals

We analyze the absolute photonic band gap in two dimensional (2D) square, triangular and honeycomb lattices composed of air holes or rings with different geometrical shapes and orientations in anisotropic tellurium background. Using the numerical plane wave expansion method, we engineer the absolute photonic band gap in modified lattices, achieved by addition of circular, elliptical, rectangular, square and hexagonal air hole or ring into the center of each lattice unit cell. We discuss the maximization of absolute photonic band gap width as a function of main and additional air hole or ring parameters with different shapes and orientation.     

六角蜂窝结构光子晶体异质结带隙特性研究

利用蜂窝结构光子晶体具有两个范围较大绝对带隙的特性，设计新型六角蜂窝结构光子晶体异质结，采用平面波展开和超晶胞相结合的方法来研究异质结的能带结构特性.给出异质结的结构和相应的能带图，分析异质结界面传导模，研究两侧结构作横向拉开和侧向滑移时对传导模的影响，讨论这些结构的实际可行性.计算结果表明，没有任何晶格移动，此种结构异质结在绝对带隙中就有导模存在，两边晶格横向拉开对导模影响较大，而侧向滑移的影响则较小. 关键词： 光子晶体 异质结 光子带隙 超晶胞     

Position calculation of the frequency band gap in the finite photonic crystal with multiple alternations using boundary element method

In this paper, the wave transmission from finite photonic crystals with multiple alternations is investigated using boundary element method (BEM). Since that, in these structures the alternation is not in all directions of space; the investigations of the frequency band gap with desired accuracy are not practical by analytical methods. Also, the frequency dispersion of dielectric rods is an effective parameter in photonic crystals, which this effect in our calculations has been considered. Due to the high capabilities of the BEM, the transmitted wave spectrum in the photonic crystal is calculated by changing the geometrical and optical parameters of the photonic crystal and applying more alternation in its structure and the position and width of the frequency band gap is investigated. Then, it is assumed that the photonic crystal with an arbitrary angle is rotated around the axis which is perpendicular on the crystal cross section and then, it is irradiated with a plan wave. The band gap of the photonic crystals with the desired structure, desired rotation angle and multiple alternations have been solved. Very low information volume, high speed and accuracy during the calculation and useable for any desired structures are the characteristics of this method.     

Theoretical study of relative width of photonic band gap for the 3-D dielectric structure

Calculations for the relative width (Δω/ω₀) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is useful for the understanding of photonic crystals and occurrence of the photonic band gap.     

Photonic crystal waveguide directional couplers as wavelength selective optical filters

Waveguide directional couplers, formed by two closely spaced linear defect waveguides in a two-dimensional photonic crystal of air holes in a semiconductor matrix, are numerically studied using plane wave expansion and finite difference time domain methods. The coupling lengths are on a wavelength scale and show a strong wavelength dependence, allowing for the design of compact wavelength selective optical filters. Applications as a channel interleaver for the 1.55 μm wavelength range and as a micrometer sized 1.31/1.55 μm wavelength demultiplexer are presented.     

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用时域有限差分法研究了电磁波在等离子体光子晶体中的传播特性。数值模拟中使用完全匹配层吸收边界条件,计算了电磁波通过等离子体光子晶体的反射和透射系数。讨论了等离子体密度、等离子体温度、介电常数比和引入缺陷层对等离子体光子晶体光子带隙的影响。     

一维Al/SrF2低温超导体-电介质光子晶体能带结构

基于二流体电子模型和平面波展开法,计算了一维Al/SrF2超导体-电介质光子晶体的能带结构.结果表明:随着超导层厚度的增加,第一光子带隙中心频率和截止频率均发生蓝移,且第一带隙宽度逐渐增加到一个峰值后又逐渐变窄.更重要的是,在低于临界温度的超低温环境中,温度的微小变化,对该类光子晶体的带隙宽度、中心频率以及截止频率均有...     

The influence of shape and orientation of scatterers on the photonic band gap in 2D metallic photonic crystals

Using the revised plane wave method, we have calculated the photonic band structures of 2D metallic photonic crystals composed of parallel metallic rods in air background and air holes drilled in metal background. We discuss the maximization of gap-to-midgap ratio as a function of scatterer parameters with different shapes and orientations in three types of lattices.     

超窄带和梳状多通道光子晶体滤波器设计

 设计了一种因掺杂而具有超窄带滤波特性的光子晶体滤波器和一种复周期结构的梳状多通道光子晶体滤波器。在两种均匀介质交替分布的周期结构中间插入一层折射率不同的介质膜后,通过传输矩阵法的数值计算,发现采用前后不对称的周期结构并调节参数,可以在1 550 nm处找到一个透射率接近100%的极窄的透过峰,因而可得到一种超窄带光子晶体滤波器。另外,在以高低两种折射率的介质交替分布,并以两种单独的单元周期合并组成一个复周期,然后进行周期重复构成的光子晶体中,利用通道数等于复周期数减1的规律,并配合各层厚度的调节,设计出在1 550 nm附近梳状8通道和16通道的光子晶体滤波器,各通道透过峰的透射率均接近100%,由此设计出一种梳状多通道光子晶体滤波器。     

电子密度对等离子体光子晶体禁带特性的影响

从Maxwell方程出发,采用类似于量子力学Kronig-Penney模型求解周期势的方法,结合双水电极介质阻挡放电的实验结果,研究了电子密度ne对一维等离子体光子晶体禁带特性的影响。研究发现:电子密度对等离子体光子晶体光子禁带的位置和宽度均有重要的影响;等离子体光子晶体的禁带宽度随电子密度的增加而增大,增长速率为电子密度的函数;等离子体光子晶体的截止频率、光子禁带边缘频率随电子密度的增大而增大。给出了当等离子体光子晶体具有显著禁带宽度时的电子密度的理论临界值。