Noncolinear Second-Harmonic Generation Pairs and Their Scatterings in Nd3+:SBN Crystals with Needle-Like Ferroelectric Domains

Second-harmonic generation in Nd3＋ ：SBN crystal with needle-like ferroelectric with aperiodic domain structures is investigated. Two pairs of second harmonic （SH） waves appearing in lines are observed in unpoled Nd3＋ ：SBN crystals with aperiodic needle-like domains. A pair of SH waves emit from the exit face, whose intensities are angle-dependent. The angular dependence is corresponding to the spatial frequency spectrum of the aperiodic domain structure. Another pair of SH waves emit from both the side surfaces, which are mainly the scattered SH waves by needle-like domain walls and obey the theory of Rayleigh scattering.

Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method

The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell＇s equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.

基于二维光子晶体全光逻辑门的设计

在二维光子晶体中嵌入了线缺陷,利用线性干涉效应和波导耦合,设计了一种基于二维光子晶体的同或门和与非门结构。主要采用平面波展开法对该二维光子晶体的能带结构进行分析,采用时域有限差分法,结合线性干涉效应,在Rsoft平台对所设计的同或门和与非门进行稳定电场图和归一化功率仿真。仿真结果标明:设计的同或门对比度高达29.5 dB,响应时间为0.073 ps,数据传输速率为13.7 Tbit/s;设计的与非门对比度高达24.15 dB,响应时间为0.08 ps,数据传输速率为12.5 Tbit/s。这些结果表明所设计的结构对比度高、响应时间短和数据传输速率快。

具有单晶到单晶转化的Cu(Ⅰ)配合物的发光性质

选用2-(N,N-双(二苯基膦基甲基))胺基吡啶(bdppmapy)为膦配体、二吡啶并[3,2-a∶2',3'-c]吩嗪(dppz)为氮配体、[Cu(CH_(3)CN)_(4)]BF_(4)为铜盐,在常温下进行反应,制备了3种新型Cu(Ⅰ)配合物,分别为[Cu(dppz)(bdppmapy)]_(2)(BF_(4))_(2)·H_(2)O (Cu BF_(4)-1)、[Cu(dppz)(bdppmapy)]BF_(4)(Cu BF_(4)-2)和[Cu(dppz)(bdppmapy)]BF_(4)(Cu BF_(4)-3)。获得了Cu BF_(4)-1和Cu BF_(4)-3的单晶,发现了单晶到单晶转化过程的现象,并探究了溶剂分子的存在对配合物结构和光物理性能的影响。通过单晶X射线衍射确定配合物Cu BF_(4)-1和Cu BF_(4)-3的结构,使用粉末X射线衍射(PXRD)、红外光谱(IR)和核磁共振氢谱/磷谱(~1H/^(31)P NMR)对合成的3个配合物进行结构表征。对配合物进行紫外可见吸收光谱(UV-Vis)、荧光光谱、荧光寿命及量子产率等光物理性质的表征和分析,比较了配合物发光性质的差异,探讨了溶剂分子对配合物结构和光物理性质的影响规律。太赫兹时域光谱对配合物的研究提供了帮助。

KDP晶体微塑性域增强金刚石切削方法研究

针对KDP在SPDT切削过程中容易产生凹坑、划痕、裂纹等表面缺陷问题,提出利用热激励的方式增大KDP晶体塑性切削域深度,降低各向异性、机床运动误差、环境振动等因素对加工过程的影响,进而提高SPDT切削加工过程稳定性的方法。通过纳米压痕试验获得了KDP晶体表面在不同温度状态下的硬度和脆塑性转变深度变化规律,并在SPDT机床上采用金刚石刀具开展了KDP晶体飞切划痕实验,进一步验证了适当提高KDP晶体温度可以增大KDP晶体脆塑性转变临界切削深度。在此基础上,对KDP晶体开展了不同温度状态下的切削实验,实验结果表明在相同工艺参数下,随着温度的升高,表面粗糙度Sa值从3.2nm降低至1.6nm。

磁化等离子体交替隐式时域有限差分法

针对传统显式时域有限差分法仿真各向异性磁化等离子体时,时间步长会受到柯朗-费里德里希斯-列维(Courant-Friedrich-Levy,CFL)条件限制的问题,采用拓展的无条件稳定交替隐式时域有限差分方法(alternating-direction-implicit finite-difference time-domain,ADI-FDTD)对无限大磁化等离子体进行数值仿真。该方法在传统两步法基础上增加2个子时间步,同时仍保持无条件稳定的特性。实验结果表明:反射和透射系数与理论值吻合较好。与普通时域有限差分方法相比,该方法能够高效仿真等离子体光子晶体,并且具有较高的精度和无条件稳定的特性。

光子晶体光纤及其在太赫兹波段的应用

太赫兹(Terahertz, THz)技术作为一项非常重要的交叉前沿学科,给环境检测、生物医学、空间通信等领域带来了深远的影响,但因为THz波导传输性能的影响,THz技术综合发展仍然受到一定限制。光子晶体光纤(Photonic Crystal Fiber, PCF)作为一种新型THz波导,拥有无限单模特性、色散灵活可调、可控的非线性、高双折射等特性,极大的促进了THz技术的发展。首先根据PCF的结构特点总结了实芯PCF(Solid Core PCF, SC-PCF)和空芯PCF(Hollow Core PCF, HC-PCF)各自的发展历程、导光机理和光学特性;其次,梳理了用于THz波导的PCF存在的问题以及对应的解决方法;然后,着重介绍了PCF在THz时域光谱、THz传输与通信以及THz光纤耦合传感中的应用;最后,对PCF在THz技术的应用做了总结与展望。

边角Zara Domain及其改善研究

研究了大尺寸TFT-LCD显示器制造工艺中LC Pattern对边角Zara domain的影响。实验表明,当大尺寸TFT-LCD显示器制作工艺中LC Pattern中边角处无液晶滴时,边角Zara domain发生率高,当LC Pattern在边角处添加液晶滴时,边角Zara domain发生率降低,通过调整边角处液晶滴到玻璃基板有效面积的距离,到一定范围时边角Zara domain明显降低,通过优化,确定当使用LC Pattern 5时,边角Zara domain发生率最低,为2.5%,经过高温炉处理后,边角Zara domain完全消失。

LOW MACH NUMBER LIMIT OF A COMPRESSIBLE NON-ISOTHERMAL NEMATIC LIQUID CRYSTALS MODEL

In this paper, we study the low Mach number limit of a compressible nonisothermal model for nematic liquid crystals in a bounded domain. We establish the uniform estimates with respect to the Mach number, and thus prove the convergence to the solution of the incompressible model for nematic liquid crystals.

A Study of Properties of the Photonic Band Gap of Unmagnetized Plasma Photonic Crystal

In this study, the propagation of electromagnetic waves in one-dimensional plasma photonic crystals （PPCs）, namely, superlattice structures consisting alternately of a homogeneous unmagnetized plasma and dielectric material, is simulated numerically using the finite-difference time-domain （FDTD） algorithm. A perfectly matched layer （PML） absorbing technique is used in this simulation. The reflection and transmission coefficients of electromagnetic （EM） waves through PPCs are calculated. The characteristics of the photonic band gap （PBG） are discussed in terms of plasma density, dielectric constant ratios, number of periods, and introduced layer defect. These may provide some useful information for designing plasma photonic crystal devices.

Design, Simulation &Optimization of 2D Photonic Crystal Power Splitter

A very compact (80 - 100 μm2) integrated power splitting devices with two outputs (1 × 2), four outputs (1 × 4) and six outputs (1 × 6) channel has been designed, simulated and optimized for Telecommunication purpose with T-Junction, Y-Junction, PC line defect waveguides integrated with multimode interference block (PCLD-MMI) and multiple line defect PC waveguides (MLDPCW) configurations. The optical modeling of these proposed structures was investigated by finite difference time domain (FDTD) simulation. With the optimization of the parameters (Hole Radius, R = 0.128 μm, Input Diameter, D = 1.02 μm, Input wavelength, λ = 1.55 μm, Substrate Reflective Index, nsub = Si(1.52), Photonic Crystal Material, npcs = InAs(3.45), and Rectangular crystal structure), 1 × 2 for Y-Junction (100%), 1 × 4 for T-Junction (92.8%) and 1 × 6 configuration for MLDPCW (81%) show maximum power transmission.

Crystal Structure of the Fab Fragment of an Anti-factor IX Antibody 10C12

10C12 is an anticoagulant antibody identified from a phage display single-chain Fv human antibody library. It can be directed at the calcium-stabilized Gla domain of Factor-IX, an important coagulation factor in intrinsic pathway of blood coagulation cascade, and interfere with membrane anchoring of Factor IX, thus inhibiting blood coagulation function. 10C12 has been demonstrated as an effective anti-coagulant in attenuating thrombosis in several different animal models. Here, we report the crystal structure of the Fab fragment of 10C12. The crystal contains two Fab molecules in the asymmetric unit with identical conformation, forming a lattice with large cavities. In addition, comparison of this free Fab with the antigen-bound structure of 10C12 shows no change in CDR conformations and the relative disposition of the variable subunits of H and L chains, suggesting the rigid conformation of this 10C12 Fab and a lock-and-key mechanism of antibody-antigen recognition for 10C12.

Bandgap characteristics of 2D plasma photonic crystal with oblique incidence:TM case

A novel periodic boundary condition （PBC）, that is the constant transverse wavenumber （CTW） method, is introduced to solve the time delay in the transverse plane with oblique incidence. Based on the novel PBC, the FDTD/PBC algorithm is proposed to study periodic structure consisting of plasma and vacuum. Then the reflection coefficient for the plasma slab from the FDTD/PBC algorithm is compared with the analytic results to show the validity of our technique. Finally, the reflection coefficients for the plasma photonic crystals are calculated using the FDTD/PBC algorithm to study the variation of bandgap characteristics with the incident angle and the plasma parameters. Thus it has provided the guiding sense for the actual manufacturing plasma photonic crystal.

Optical properties of the two-port resonant tunneling filters in two-dimensional photonic crystal slabs

We have designed and fabricated two types of two-port resonant tunneling filters with a triangular air-hole lattice in two-dimensional photonic crystal slabs. In order to improve the filtering efficiency, a feedback method is introduced by closing the waveguide. It is found that the relative position between the closed waveguide boundary and the resonator has an important impact on the dropping efficiency. Based on our analyses, two different types of filters are designed. The transmission spectra and scattering-light far-field patterns are measured, which agree well with theoretical prediction. In addition, the resonant filters are highly sensitive to the size of the resonant cavities, which are useful for practical applications.

Main Factors for Affecting Photonic Bandgap of Photonic Crystals

The factors affecting one dimensional （1D） and two dimensional （2D） photonic crystals （PhCs） are systemically analyzed in this paper by numerical simulation. Transfer matrix method （TMM） is employed for 1D PCs, both finite difference time domain method （FDTD） and plane wave expansion method （PWE） are employed for 2D PCs. The result shows that the photonic bandgaps （PBG） are directly affected by crystal type, crystal lattice constant, modulation of refractive index and periodicity, and it is should be useful for design of different type photonic crystals with the required PBG and functional devices. Finally, as an example, a near-IR 1D PCs narrow filter was designed.

Engineering the light propagating features through the two-dimensional coupled-cavity photonic crystal waveguides

This paper studies the propagating characteristics of the electromagnetic waves through the coupled-resonator optical waveguides based on the two-dimensional square-lattice photonic crystals by the finite-difference time-domain method. When the traditional circular rods adjacent to the centre of the cavities are replaced by the oval rods, the simulated results show that the waveguide mode region can be adjusted only by the alteration of the oval rods＇ obliquity. When the obliquity of the oval rods around one cavity is different from the obliquity of that around the adjacent cavities, the group velocities of the waveguide modes can be greatly reduced and the information of different frequencies can be shared and chosen at the same time by the waveguide branches with different structures. If the obliquities of the oval rods around two adjacent cavities are equal and they alternate between two values, the group velocities can be further reduced and a maximum value of 0.0008c （c is the light velocity in vacuum） can be acquired.

Fabrication of high-quality three-dimensional photonic crystal heterostructures

Three-dimensional photonic crystal （PC） heterostructures with high quality are fabricated by using a pressure controlled isothermal heating vertical deposition technique. The formed heterostructures have higher quality, such as deeper band gaps and sharper band edges, than the heterostructures reported so far. Such a significant improvement in quality is due to the introduction of a thin TiO2 buffer layer between the two constitutional PCs. It is revealed that the disorder caused by lattice mismatch is successfully removed if the buffer layer is used once. As a result, the formed heterostructures possess the main features in the band gap of constitutional PCs. The crucial role of the thin buffer layer is also verified by numerical simulations based on the finite-difference time-domain technique.

Study on incident laser modulation using surface micro-defects on KH_2PO_4 crystal

KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries （e.g., width, morphology, and depth of defects） are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 p-m. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μm for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.

Analysis of photonic crystal on LED extraction efficiency

Because of its very low light extraction efficiency(LEE),LED is limited to be widely used under the condition of the internal quantum efficiency which up to 90%.In order to fullfill the design of a more efficient GaN-based blue light LED,the model including deeply etched surface photonic crystals(PhCs)LED is discussed using mode analysis method from light waveguide theory.The distributions of all order modes in GaN layer are obtained by the effective index approximation.The light extraction efficiencies are also calculated by finite-difference time-domain method(FDTD).The emulated results fully coincide with the former analysis.Because the manufacture of the surface photonic crystal is feasible,the work can be very meaningful to design and manufacture the high efficiency GaN-based blue light LED in factory for a large amount.

温变小空间下高频六维气动力天平研究

风洞天平是飞行器模型风洞试验的关键测力设备。近年来随着飞行器模型设计复杂度及流场速度提高,对天平的体积、温度敏感性及动态特性要求越来越高。为提高天平的动态性能的同时减小其尺寸,文中提出了石英晶片分区面域电荷采集的压电式六维力测量方法。针对风洞高速流场的气动热影响,选择不同天平材料进行热力学仿真分析。为提高天平刚度,对天平部件的结构尺寸进行参数化仿真。最后对压电杆式天平进行静动态标定及温度敏感性实验,结果表明:天平非线性误差不超过1.31%,重复性误差低于1%,固有频率高于2700 Hz,温度影响相对变化量为0.5%,满足测试需求。