Band gap structure of disordered chiral photonic crystals

Based on the non-symmetric transmission-line method, the band gap structure of disordered chiral photonic crystals (CPC) has been investigated. The influence of the chiral parameters, the disorder, the periods and the refractive index on the band gap structure has been discussed. It is found that the photonic band gap (PBG) in CPC is more obvious than that in the conventional photonic crystals, and the PBG can be increased by increasing the periods or the contrast of the refractive index of the two media. It is also found that the existence of disorder will influence the band edge of the PBG, and such influence will increase with the increment of periods or the contrast of the refractive index of the two media.     

由球形原子构成的多种周期性介电结构的光子能带计算

采用矢量平面波方法计算了由球形空气原子构成的体心立方结构和六角密堆结构的光子能带，两种结构下都看到了贯通整个布里渊区的禁带。本文预言周期性介电结构的最大折射率调制度和最大禁带宽度对应于同样的原子体积分数，而且这个最佳的原子体积分数是结构无关的。文中还计算了由各向异性介电小球构成的面心立方结构的光子能带并看到了禁带，这与各向同性介电小球构成的面心立方结构很不相同。     

用特征矩阵法研究一维激光全息光子晶体的禁带特性

介质中传播方向相反的2束激光干涉可形成具有一维周期结构的体积全息图,而这种全息图可以看作一维光子晶体,称为一维激光全息图光子晶体,用特征矩阵法研究了一维激光全息图光子晶体的透射谱中的禁带随入射角、记录波长、介质折射率、折射率调制度的变化规律。结果表明：当入射角变大,激光波长、介质折射率及介质折射率调制度变小时, 禁带的位置向短波方向移动, 禁带宽度减小。     

Demonstration of tunable complex refractive index of graphene covered one dimensional photonic crystals

Here, we report tunable complex optical properties of one dimensional photonic crystal covered by graphene layer, as a new optical material, in the visible spectral range. For this purpose, we fabricate two different structure as one dimensional photonic crystal, with photonic band gap which centered at 650 nm, by electron gun deposition method and the chemical vapor deposition has been used to synthesize graphene top layer. To demonstrate the optical properties of our two photonic crystals affected by graphene layer, we use the reflectance spectra of the samples as a function of incidence angle. Because the sufficient sensitivity of the refractive indices of the samples, we extract the real and imaginary part of these parameters in all of visible region as a tunable complex refractive index. Our results show that we have sufficient change due to excited plasmons in graphene layer by Bloch wave of photonic crystal which is very useful for sensor applications.     

Extension of photonic band gaps in one-dimensional photonic crystals

A method is proposed for extending photonic band gaps by constructing periodic structures from two or more consecutively located photonic crystals with different lattice constants or filling factors. The photonic band gaps with a maximum extension are predicted by superposing the photonic band gap maps on one another. It is demonstrated that both the lowest and higher order band gaps can be merged in photonic crystals with a high refractive index contrast.     

Method for retrieving the refractive index of ordered particles from data on the photonic band gap

A method for retrieving the refractive index of spherical particles arranged into ordered structures is proposed. It is based on the solution of the inverse problem using data on the photonic band gap. The solution has been obtained within the quasi-crystalline approximation of the multiple wave scattering theory and the transfer-matrix method. Quantitative results are presented for systems of silicon oxide particles. The effective refractive indices of synthetic opal particles have been found from the available experimental data on the spectral position of the photonic band gap. The described technique is applicable for retrieving not only the refractive index of particles but also other characteristics of ordered particulate structures from the coherent transmittance spectra.     

介质柱型二维Triangular格子光子晶体的禁带特性

采用平面波展开法数值计算了空气背景中由圆形、正六边形和正方形介质柱构造的二维三角晶格光子晶体禁带结构,并研究了介质方柱旋转角度、介质折射率和填充比对完全光子禁带宽度的影响.结果表明,在低频区,介质方柱旋转17°时,出现最大完全光子禁带,且最大禁带宽度随介质折射率的变化较为稳定.在高频区,介质方柱旋转30°时,完全光子禁带宽度最大;且介质材料折射率n=2.2时即出现完全光子禁带,n=2.6时,完全光子禁带达到最大.     

全息制作不同晶面取向光子晶体模板

用单向光入射和单次曝光的激光全息技术制作了类金刚石结构, 此类金刚石结构有宽完全带隙和低介质折射率要求等优点. 在同一种光束配置下，引入恰当的匹配棱镜，用激光全息技术制作了大面积的类金刚石光学晶格不同晶面取向的亚微米周期结构. 满足如负折射效应等研究中所需的特殊晶面取向要求. 关键词： 激光全息技术 光学晶格 光子晶体     

一维函数光子晶体的研究

本文提出一种新型函数光子晶体, 其折射率是空间位置函数. 由费马原理, 我们给出光在一维、 二维和三维函数光子晶体中的运动方程, 以及一维函数光子晶体的色散关系、 带隙结构和透射率, 再利用传输矩阵理论研究函数光子晶体周期数、 入射角和介质层的厚度等对透射率和禁带结构的影响, 计算发现通过选择不同的折射率空间分布函数, 可以得到比传统光子晶体更宽或更窄的禁带结构. 这样为我们设计不同带隙结构的光子晶体提供理论依据.     

Tuning of the photonic band gaps and the reflection spectra of a one-dimensional photonic crystal based on silicon and a liquid crystal

The reflection spectra and the photonic band gaps of a one-dimensional composite photonic crystal are calculated for different filling factors (the ratio of the thickness of a silicon layer to the lattice constant A). A change in the refractive index of the filler in a photonic crystal leads to the shift of both edges for certain side photonic bands. It is shown that, with a change in the refractive index from 1.49 to 1.69, the shift of the edges (the tuning effect) can reach the value A/λ = 0.04 for the main photonic band and 0.08 for a side band. An additional criterion for designing a photonic crystal is the estimation of the sharpness of the edges of photonic bands in the reflection spectra.     

Beyond butterflies—the diversity of biological photonic crystals

When biological photonic crystals are discussed, butterfly photonic crystals are often cited as representative; in fact, numerous diverse biological photonic crystals exist and butterfly photonic crystals have several quirks when compared with others, with the consequence that considering them typical is in many ways unhelpful. In this paper, we give an overview of biological photonic crystals and discuss their typical features, specifically with regard to their periodicities, geometries, chemical compositions, the wavelengths they reflect and their band gaps. The low refractive index contrast and low mean refractive index: a universal feature of biological photonic crystals compared with artificial ones is highlighted and attention is drawn to their comparatively complex band diagrams.     

Optical refractometer based on large-core air-clad photonic crystal fibers

A large-core air-clad photonic crystal fiber-based sensing structure is described, which is sensitive to refractive index. The sensing head is based on multimodal interference, and relies on a single-mode/large-core air-clad photonic crystal fiber (PCF)/single-mode fiber configuration. Using two distinct large-core air-clad PCF geometries-one for refractive index measurement and the other for temperature compensation, it was possible to implement a sensing head sensitive to refractive index changes in water as induced by temperature variations. The results indicated the high sensitivity of this sensing head to refractive index variations of water, and a resolution of 3.4×10(-5) refractive index units could be achieved.     

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     

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.     

等效折射率为非-1时的亚波长成像

本文采用硅柱子周期性排列构成六角结构光子晶体,用平面波展开方法和FDTD方法研究表明,此结构光子晶体存在等效折射率接近-1的频率区域.在等效折射率趋于-1但不等于-1时,此光子晶体平板结构超透镜能形成一个非近场的像.模拟还发现,此结构平板光子晶体等效折射率为非-1时,可以亚波长成像. 关键词： 负折射 光子晶体 亚波长 成像     

Enhanced complete photonic band gap in the optimized planar diamond structure

The diamond photonic crystal with dielectric rods has been modified to enlarge the fundamental band gap. By planarizing the diamond structure and reducing the thickness of the hexagonal meshes, the band gap can be increased substantially. The band gap is 29% for a refractive index contrast of 3.6. The modified structure is amenable to fabrication at optical and infrared wavelengths using state-of-the-art silicon-processing methods. Transfer matrix calculations demonstrate a large attenuation within the band gap.     

Numerical demonstration of slow light tuning in slotted photonic crystal waveguide using microfluidic infiltration

Tuning of the operating wavelength of slow light in the slotted photonic crystal waveguide using microfluidic infiltration has been investigated. Using 2D plane wave expansion method, we numerically demonstrate that the operating wavelength can be shifted from the C to L band, simply by choosing the refractive index of the infiltrated fluid. It is also found that, as the refractive index of the infiltrated fluid changes, the group velocity dispersion has slight variation at different operating wavelength. This design opens the possibility for post-fabrication scheme of tuning the operating wavelength of slow light in slotted photonic crystal waveguide, and allows the device to be optimized for different applications.     

带有KTP缺陷的2维光子晶体设计与能带特性

 设计了一种通过改变缺陷介质折射率实现能带特性改变的可调谐2维光子晶体激光器微腔,在光子晶体中引入点缺陷磷酸氧钛钾(KTP),在KTP两端施加交流电场控制KTP晶体折射率变化。实验过程中观察到了正方排列的光子晶体随着KTP 晶体折射率逐渐增大,晶体禁带数量减少,且向归一化频率小的方向移动,禁带宽度基本不变;而三角排列的晶格能带随着KTP折射率增大,禁带逐渐变窄,且有向低频方向移动的趋势。用平面波展开法分析了晶体的能带结构,得到理上的描述。     

Fabrication and characterization of three-dimensional metallodielectric photonic crystals for infrared spectral region

We propose a technique for the realization of three-dimensional metallodielectric photonic crystals based on fabricating polymeric structures using the interference lithography followed by the magnetron deposition of a gold nanolayer. The infrared reflectance spectra of the fabricated photonic crystals are studied. The spectrometry and finite-difference time-domain modeling data show that there is a photonic band gap centered at the wavelength approximately equal to the photonic crystal period.     

Tunable highly birefringent photonic bandgap fibers

A novel tunable highly birefringent photonic bandgap fiber (PBGF) is designed theoretically by filling its air holes with high-index material. The transmission band can be continuously tuned by changing the refractive index of the filling material. Accordingly, the tunable modal birefringence and polarization mode dispersion of the PBGFs are investigated by adjusting the refractive index of the filling material. Furthermore, we have also analyzed the effect of surface modes in the photonic bandgap on the characteristics of the tunable PBGFs. The simulation results show the feasibility of constructing birefringence-tunable photonic crystal fibers and related fiber devices in practical applications.