新型光子晶体THz滤波器

提出了一种新型基于光子晶体的太赫兹滤波器,该滤波器在线缺陷中设计了由三个点缺陷构成的谐振腔,能够实现双波长的高效滤波功能。文中使用平面波展开法(PWM)分析了正方晶格光子晶体的带隙结构,并利用时域有限差分法(FDTD)研究了滤波器的一些性能指标。仿真结果表明,该新型滤波器能够把频率为3.413 THz和3.222 THz的太赫兹波滤出,并且具有滤波带宽窄、体积小等优点。     

Simulation of the spatial pattern and band-gap structure of holographic photonic crystals

Simulation software of the spatial pattern and band-gap structure of the holographic photonic crystals is developed for the research—education purposes. Friendly GUI and training technique elaborated. Examples of the 1D–3D model structures of photonic crystals and their transmission spectrums are given. The article is published in the original.     

Terahertz switch and polarization controller based on photonic crystal fiber

Theoretical studies on liquid crystal filled photonic crystal fiber(LC-PCF)are presented.The eects of electric birefringence of liquid crystal(LC)in the LC-PCF and the transmitting properties of photonic crystal fiber(PCF)are investigated by using the full vector plane wave expansion and beam propagation method.The simulation results show that the electrically controlled LC-PCF can act as not only a terahertz(THz)switch with about 0.55 THz bandwidth,but also a tunable polarization controller for changing the polarization state of the fundamental mode.     

基于Matlab的光子晶体波导仿真研究

本文首先介绍了光子晶体波导的原理,然后分析时域有限差分法微分方程及边界条件,最后运用matlab语言实现二维光子晶体波导的仿真。     

基于Matlab的光子晶体波导仿真研究

本文首先介绍了光子晶体波导的原理，然后分析时域有限差分法微分方程及边界条件，最后运用matlab语言实现二维光子晶体波导的仿真。     

Optimization of the inhibition of atmospheric window emission using photonic crystals

Transfer matrix method is used to discuss the effect inhibition of photonic crystals on atmospheric window emission(ε-14 μm).According to the optical characteristics of the materials,germanium and zinc sulfide are used as the composing materials.The structure of the photonic crystals is optimized,and the optimal thickness values of the germanium and zinc sulfide are 0.63 and 1.11μm respectively while the ratio of optical thickness is 1:1 and the period is 8.The photonic crystals are prepared by evaporation ...     

Photo‐aligned photonic ferroelectric liquid crystal fibers

Preliminary studies of photonic crystal fibers (PCFs) partially infiltrated with photo‐aligned ferroelectric liquid crystals (FLCs) under the influence of external electric field are reported. The proper alignment of the FLC molecules is achieved by generating a photo‐aligning layer on the inner side of the PCF microcavities. The sulfonic azo dye, which is used as an alignment layer, offers a variable anchoring energy depending on the irradiation energy, and thus, a good control on the FLC alignment inside microchannels is possible. Moreover, a state of polarization of the light being guided inside the PCF infiltrated selectively with FLC changes under the influence of external electric field.     

二维光子晶体传输特性的时域精细积分法

本文研究了二维光子晶体的时域精细积分法,并对其精度、效率、以及稳定性进行分析.从麦克斯韦方程的微分形式出发,利用Yee元胞将空间微分算子近似为差分算子,结合边界条件及激励源的表达式得到一组关于时间的常微分方程.对时间进行精细划分,使用精细积分算法求解常微分方程组.结合通解与激励源的特解得到光子晶体两端的反射场及透射场分布,进而通过傅里叶变换求得二维光子晶体的传输特性.数值算例表明,本文方法具有准确、稳定、高效的特点.     

向列相液晶缺陷光子晶体可调谐滤波器的研究

在一维光子晶体中引入向列相液晶作为缺陷层,用电场改变液晶分子的取向,形成光子晶体可调谐滤波器.用传输矩阵法研究了液晶缺陷光子晶体的可调谐滤波特性,模拟计算了电压和液晶材料参数对滤波器透射谱的影响.结果表明,改变电压能容易改变光子晶体滤波器透射峰的位置、强度、个数和带宽,表现出很好的调谐滤波功能.     

光子石墨烯多方位探测传感器研究

为了实现多方位的探测,针对光子石墨烯特殊的光传输机制,在了解光子石墨烯谷依赖波束输运的基础上,选择光子石墨烯的相关参数,并设计了合适的结构模型,用COMSOL软件对其进行仿真计算.结果表明:在二维光子石墨烯结构中放置点源,点源发射的光束在平面内可以沿6个方向进行传输,此结构用于传感器即可以实现多方位的探测,可为多方位探测传感器的研制提供新的思路.     

Multifunctional glassy liquid crystals for photonics

Abstract— As an emerging class of photonic materials, morphologically stable glassy liquid crystals, were developed following a versatile molecular design approach. Glassy cholesteric liquid crystals with elevated phase‐transition temperatures and capability for selective‐wavelength reflection and circular polarization were synthesized via deterministic synthesis strategies. Potential applications of glassy cholesteric liquid crystals include high‐performance polarizers, optical notch filters and reflectors, and circularly polarized photoluminescence. A glassy nematic liquid crystal comprising a dithienylethene core was also synthesized for the demonstration of nondestructive rewritable optical memory and photonic switching in the solid state.     

Cholesteric liquid crystals for detection of organic vapours

Studies on the use of cholesteric liquid crystals (CLCs) as sensing phase for detection of organic vapours in air are described. Stock solutions of 1.0% (w/v) cholesteryl nonanoate (CN) and cholesteryl chloride (CC) were prepared in tetrahydrofuran. Binary mixtures, with compositions ranging from 0.18 to 0.25% of CC and 0.82–0.75% of CN, respectively, were prepared by appropriate mixing of the stock solutions. Films were cast by pipetting three 10 μl aliquots of the CLC solution mixture onto a glass disk, whose reverse side was made black to absorb unscattered light. The glass disk was adapted to the common end of a bifurcated optical fibre bundle and placed in a glass vial, which provided a headspace of organic vapours. Measurements were carried out at 27±1 °C, a temperature in which the CLC mixtures maintain their liquid crystalline properties. The responses of the CLC mixtures to vapours of ethanol, acetone, benzene, pyridine and hexane were investigated. The colour of the sensing phases depended on their compositions and exposure to organic vapours gives rise to a change in the optical characteristics of liquid crystals. It was found that the CLC layers containing 0.23–0.25% of CC had no significant change in optical properties when exposed to organic vapours and that ethanol did not cause any optical changes in the liquid crystal layers. Benzene as well as hexane always turned all the coloured liquid crystalline layers to colourless. The CLC layers exhibited different behaviours to vapours of acetone and pyridine. For example, the wavelengths of maximum scattering for the 0.19% CC layer were 530 nm in air, 545 nm in pyridine and 580 nm in acetone. The CLC layers showed reversibility. The lifetimes of these layers (interval of time in which the liquid crystalline phase exists, before crystallisation) were investigated by employing acetone and n-hexane vapours. Average lifetimes of 14–15 min were found for films in contact with these vapours, while a lifetime of 205 min was possible when the CLC film was exposed to air.     

Lattice-parameter effects on diffracted transmission of GaN two-dimensional square-lattice photonic crystals

The lattice-parameter effects on the diffracted transmission of GaN square-lattice photonic crystals (2PhC) at the wavelength of 460 nm were studied by using a rigorous coupled wave analysis (RCWA). The impacts of lattice parameters on the diffracted transmission are calculated in the ranges for lattice pitch from 100 nm to 2000 nm,fill factor from 0.1 to 0.9 and grating height from 100 nm to 1000 nm,respectively. Our simulation results confirm that the lattice pitch is the dominant factor of the diffractio...     

Ferroelectric liquid crystals: Excellent tool for modern displays and photonics

The ferroelectric liquid crystals, because of their fast electro‐optical response, are one of the most important classes of liquid crystals. Here, in this review, we have summarized the different electro‐optical modes for ferroelectric liquid crystals. Clark–Lagerwall effect (surface stabilized ferroelectric liquid crystal), deformed helix ferroelectric (DHF) effect, electrically suppressed helix (ESH) mode, DHF orientational Kerr effect, and ESH diffraction modes have been discussed. All of the crucial features, that is, optics, electro‐optics, dynamics, and their dependence on material parameters, operational regime, and applications, have been reviewed.     

Epsilon-near-zero or mu-near-zero materials composed of dielectric photonic crystals

We theoretically demonstrate that at certain frequencies two-dimensional dielectric photonic crystals （PCs） may be regarded as either epsilon-near-zero or mu-near-zero materials. We show that the transmission through a slab of such materials upon normal incidence is normally non-unity and decays with slab thickness. However, when the incident angle increases slightly, the transmittance experiences a dramatic increase due to the Brewster effect. The combination of the tunneling and resonance effects makes such materials good candidates for almost perfect bending waveguides and cloaking in waveguides. The zero index also enables applications of focusing and directive emission. At last, the distinction between the single-zero and double-zero media is discussed. In all of the above results, the numerical simulations perfectly match with theoretical predictions from the effective medium analysis.     

基于镜像异质三周期光子晶体介观压光效应的加速度传感器*

利用镜像异质三周期光子晶体的介观压光效应,用其来代替传统压阻式加速度传感器中的压敏电阻膜,设计出一种新型的高灵敏度加速度传感器。该加速度传感器采用四端固定梁结构,有效地消除了偏轴效应,具有很好的稳定性,在室温下其可测量的加速度范围为0~137gn。利用ANSYS软件对所设计的光子晶体加速度传感器进行静态分析和模态分析。可以看出在悬臂梁根部具有最大的应变值,而且第一模态频率与其他模态频率相差较大,可以有效降低交叉耦合。将光子晶体置于悬臂梁根部具有最大的感应灵敏度。这种加速度计具有很大的优势运用到以后的航天,军事等领域。     

Electrically suppressed helix ferroelectric liquid crystals for modern displays

In this article, we disclose electrically suppressed helix ferroelectric liquid crystal (ESHFLC) that is characterized by high optical quality and fast response time at the cost of extremely small driving voltage. These unique features of the ESHFLCs are highly sensitive to the anchoring energy that should be smaller and comparable to the elastic energy of the ferroelectric liquid crystal helix. The photo alignment, which offers good control on the anchoring energy by means of the irradiation energy, is critically important to lock the optimum parameters of the ESHFLC display cell. An example of field sequential color display with the frame frequency of 240 Hz at the driving voltage of 2 V has been demonstrated.     

Optimization of liquid crystals for television

Abstract— LCD TVs have dramatically improved in performance during the last 2 years. At the same time, the sale prices decreased by more than 50%. Together with the introduction of digital terrestrial broadcasting, this resulted in increasing sales of LCD TVs. This paper gives an overview of the main liquid‐crystal display (LCD) technologies used for TVs. We discuss key materials, synthesis, structural property relationships, and the optimization of LC mixture properties. For all technologies, we have achieved fast‐switching LC mixtures (16 msec). Novel materials for LC mixtures for the next generation of superior performance LCD TVs with 8‐msec switching times are shown.     

Refractive‐index matching between liquid crystals and photopolymers

Abstract— Refractive indices of two photocurable polymers, NOA65 and NOA81 (Norland Optical Adhesive), and two series of Merck liquid crystals, E‐series (E44, E48, and E7) and BL‐series (BL038, BL003 and BL006), and two UCF high‐birefringence liquid‐crystal mixtures were measured using an Abbe refractometer in the visible spectral region and 15–55°C temperature range. Some liquid crystals have excellent index matching with NOA65 in the red, while some fit better in the blue spectral region. To validate this index‐matching property found in the material level, we prepared some polymer‐dispersed liquid‐crystal devices. Good correlations between material and device performances are obtained.