Characteristics of vertical bent coupling between straight and curved rectangular optical waveguides

In terms of the coupled mode theory (CMT) and the transfer matrix method, we present a technique and relative formulas including the bent coupling coefficient, amplitude coupling ratio, amplitude transmission ratio and propagation power for analyzing the vertical bent coupling between a curved rectangular waveguide and a straight one. Investigations show that the bent coupling appears in an effective coupling region by both sides of the central coupling point. Beyond this effective coupling region, however, the bent coupling is very weak, and the propagation power in the waveguide is closer to a constant. As the bent radius increases, or the thickness of the coupling layer between these two waveguides decreases, this effective coupling region becomes wider, in which the coupling behavior becomes stronger.     

耦合器分光比的精确控制

利用矩形近似理论对用熔锥法制作的耦合器分光比进行了分析。结果表明,影响分光比的主要因素为耦合区长度。给出了两者间变化的理论公式,并在实验中得到了证实。CorningSMF28光纤耦合器分光比随耦合区长度变化的实验值为0 04%/μm,实验值与理论值基本一致。通过调节耦合区长度,得到了精确的50∶50分光比的光纤耦合器。     

多层单向耦合星形网络的特征值谱及同步能力分析

随着复杂网络同步的进一步发展,对复杂网络的研究重点由单层网络转向更加接近实际网络的多层有向网络.本文分别严格推导出三层、多层的单向耦合星形网络的特征值谱,并分析了耦合强度、节点数、层数对网络同步能力的影响,重点分析了层数和层间中心节点之间的耦合强度对多层单向耦合星形网络同步能力的影响,得出了层数对多层网络同步能力的影响至关重要.当同步域无界时,网络的同步能力与耦合强度、层数有关,同步能力随其增大而增强;当同步域有界时,对于叶子节点向中心节点耦合的多层星形网络,当层内耦合强度较弱时,层内耦合强度的增大会使同步能力增强,而层间叶子节点之间的耦合强度、层数的增大反而会使同步能力减弱;当层间中心节点之间的耦合强度较弱时,层间中心节点之间的耦合强度、层数的增大会使同步能力增强,层内耦合强度、层间叶子节点之间的耦合强度的增大反而会使同步能力减弱.对于中心节点向叶子节点耦合的多层星形网络,层间叶子节点之间的耦合强度、层数的增大会使同步能力增强,层内耦合强度、节点数、层间中心节点之间的耦合强度的增大反而会使同步能力减弱.     

Characteristic Analysis of Bending Coupling Between Two Optical Waveguides

By means of the coupled mode theory and transfer matrix technique, a method is presented for analyzing the bending coupling between straight and bent rectangular waveguides, or between two bent rectangular waveguides. Calculations show that an effective coupling region exists around the central coupling point, in which the bending coupling appears, beyond which the bending coupling is very weak, and the propagation power in each waveguide becomes constant. When the bending radius becomes larger or the central coupling gap becomes smaller, this effective coupling region becomes wider, in which the coupling behavior becomes stronger.     

基于非球面透镜的空间光场光纤耦合系统研究

针对全光纤激光雷达中空间光场与单模光纤的耦合问题,设计了基于非球面透镜的望远镜光纤耦合系统.利用ZEMAX软件以单模光纤耦合效率为优化目标对其结构参量进行优化设计,然后分别用LED和激光器作为光源进行初步实验,比较直接耦合和非球面透镜耦合效果.实验结果表明,采用非球面透镜耦合可使多模光源的耦合效率比直接耦合增加约47%,与仿真结果45%非常接近,且不同芯径耦合光功率之比大略等于芯径比平方;而该耦合方式可使单模光源的耦合效率增加约20%,且耦合进不同小芯径光纤的耦合效率之比约为其芯径比平方的2.4倍,这对构建全光纤转动喇曼激光雷达系统具有重要意义.     

固体激光器与光纤激光器对光子晶体光纤棒耦合的分析与对比

耦合效率的高低与耦合后光斑的好坏直接影响着光子晶体光纤棒的放大效果,因此需要对种子光的耦合效果进行研究,选择合适的激光器作为种子源。本文对光子晶体光纤棒在固体激光器与光纤激光器两种情况下的耦合效率进行了理论分析;模拟计算了两种激光器情况下耦合效率的变化规律以及对准误差对耦合效率的影响;选择合适的透镜或透镜组,使用两种激光器对光子晶体光纤棒进行了耦合实验;对比两种激光器的耦合效果可知:固体激光器的耦合效率最高只能达到62.4%,而光纤激光器的耦合效率可以达到80%以上;在光纤激光器耦合情况下,对不同功率注入时耦合效率,以及耦合后光斑进行了实验分析。得到的实验结果对后续光纤棒的放大实验具有指导作用。     

Field coupling-induced synchronization via a capacitor and inductor

Resistor-based voltage coupling is often used to realize complete synchronization between identical nonlinear circuits while phase synchronization is investigated between non-identical nonlinear circuits (periodic or chaotic oscillation). Indeed, the coupling resistor used to consume certain Joule heat and energy before reaching the synchronization target when continuous current passed across the coupling device. In this paper, capacitor and inductor is paralleled with one coupling resistor, respectively, and the coupling devices are used bridge connection between two LC hyperchaotic circuits for investigating synchronization problems. As a result, the coupling channel can be activated to propagate energy and balance the outputs voltage from the two circuits. The dimensionless dynamical equations are obtained by applying scale transformation on the circuit equations when field coupling is switched on. It is found that the threshold of coupling intensity for reaching synchronization and the power consumption of controller can be decreased when the coupling resistor is paralleled with on capacitor or inductor. The mechanism could be that involvement of coupling capacitor(or inductor) can trigger time-varying electric field (or magnetic field), and the energy flow of field coupling via coupling capacitor (or inductor) can contribute the exchange of energy in the coupled nonlinear circuits. It can give insights to investigate synchronization on chaotic systems, neural circuits and neural networks including synapse coupling and field coupling. Finally, the experimental results on circuits are also supplied for further verification.     

微波孔缝线性耦合函数研究

 讨论了微波脉冲通过孔缝线性耦合进入腔体内的研究方法。给出了线性耦合的物理基础,定义了耦合函数，并导出了耦合函数随入射电场极化方向变化的公式。简要描述了数值求解孔缝线性耦合的时域有限差分方法以及修正算法。给出了以矢量网络分析仪HP8510C为主要设备测量耦合函数的实验方法。通过耦合函数的研究，观察到了共振效应和增强效应等现象，给出了微波孔缝耦合发生共振的普适公式。分析了测量探头对耦合函数测量的影响，验证了耦合函数随入射电场方向变化的公式。理论、数值和实验结果符合得较好。     

基于非球面透镜的空间光场光纤耦合系统研究

针对全光纤激光雷达中空间光场与单模光纤的耦合问题,设计了基于非球面透镜的望远镜光纤耦合系统.利用ZEMAX软件以单模光纤耦合效率为优化目标对其结构参量进行优化设计,然后分别用LED和激光器作为光源进行初步实验,比较直接耦合和非球面透镜耦合效果.实验结果表明,采用非球面透镜耦合可使多模光源的耦合效率比直接耦合增加约47％,与仿真结果45％非常接近,且不同芯径耦合光功率之比大略等于芯径比平方;而该耦合方式可使单模光源的耦合效率增加约20％,且耦合进不同小芯径光纤的耦合效率之比约为其芯径比平方的2.4倍,这对构建全光纤转动喇曼激光雷达系统具有重要意义.     

Describing spatiotemporal couplings in ultrashort pulses using coupling coefficients

Three coupling coefficients are defined to describe spatiotemporal coupling in ultrashort pulses. With these coupling coefficients, the first-order spatiotemporal couplings of Gaussian pulse and beam are described analytically. Also, the first-order and the second-order spatiotemporal couplings caused by angular dispersion elements are studied using these coupling coefficients. It can be shown that these coupling coefficients are dimensionless and normalized, and readily indicate the severity of spatiotemporal coupling.     

新型负耦合结构在基片集成波导滤波器中的应用

针对高性能交叉耦合基片集成波导带通滤波器的应用,提出一种新型负耦合结构,该耦合结构由两个短路耦合线设计实现,并详细分析了其特性,能够实现较弱或较强的负耦合。总结了基于特征多项式的耦合矩阵综合优化方法,并通过两个滤波器的设计进行说明。基于综合得到的两个耦合矩阵,设计了两个中心频率为10 GHz的四阶交叉耦合基片集成波导带通滤波器,第一个滤波器的归一化相对带宽为3%,负耦合结构提供交叉耦合,用于说明该耦合结构提供相对较弱的耦合强度;第二个滤波器的相对带宽为8%,负耦合结构提供主耦合,用于说明该耦合结构提供较强的负耦合强度。为了验证滤波器的实际性能,对这两款滤波器进行了加工和测试。测试和仿真结果一致性较好,表明了该负耦合结构用于高性能交叉耦合基片集成波导滤波器设计的可行性。最后讨论了弱色散交叉耦合对传输零点位置的影响。     

钾扩散耦合引起的心脏中螺旋波的变化

在某些情况下, 心肌细胞外的钾离子浓度是变化的, 钾离子的横向扩散会导致细胞外钾离子的聚集和产生钾扩散耦合, 用考虑钾扩散耦合的Luo-Rudy相I心脏模型研究了钾扩散耦合对螺旋波动力学的影响. 数值模拟结果表明: 当钾扩散耦合比较强时, 钾扩散耦合使细胞外钾离子浓度先升高, 然后做规则振荡, 导致螺旋波做无规则漫游; 观察到螺旋波的波臂宽度和频率随钾扩散耦合的强度增大而减小, 这样, 当钾扩散耦合足够强时, 钾扩散耦合可以消除螺旋波和时空混沌. 关键词： 钾扩散耦合 螺旋波 时空混沌     

Synchronization in chaotic oscillators by cyclic coupling

We introduce a type of cyclic coupling to investigate synchronization of chaotic oscillators. We derive analytical solutions of the critical coupling for stable synchronization under the cyclic coupling for the Rössler system and the Lorenz oscillator as paradigmatic illustration. Based on the master stability function (MSF) approach, the analytical results on critical coupling are verified numerically. An enhancing effect in terms of lowering the critical coupling or enlarging the synchronization window in a critical coupling space is noticed. The cyclic coupling is also applied in other models, Hindmarsh-Rose model, Sprott system, Chen system and forced Duffing system to confirm the enhancing effect. The cyclic coupling allows tuning of two coupling constants in reverse directions when an optimal control of synchronization is feasible.     

光子晶体波导定向耦合器

在完整二维光子晶体中引入线缺陷后，就形成了光子晶体波导；将时域有限差分方法(FDTD)用于光子晶体波导耦合研究，计算了不同耦合长度情形下的波导各个出口处的透过率，结果表明：光子晶体波导耦合遵循普通介质波导耦合的一般规律，也有定向耦合的功能。进一步的研究表明：对于不同的频率，光子晶体定向耦合器耦合系数是不同的，并且耦合系数和对应的频率之间近似直线关系。     

高功率微波缝隙耦合效应的试验研究

 利用高功率微波源对预设的11种不同尺寸的缝隙做了耦合效应试验，得到了这11种缝隙对试验波段的一般耦合特性。试验结果表明：窄缝的耦合效应有较强的极化特性；从波长与缝隙的长度相对关系对耦合效应的影响来看，波长与缝隙的长度相当时耦合效应最强；在UWB，L，S，X几个波段内，缝隙的宽度越窄，耦合效应越弱；缝隙的深度能明显影响其耦合效应，随缝深的增加，耦合效应逐渐减弱；辐射波脉宽变化对耦合效应基本没有影响。     

强偶合系统的弱偶合方法处理

本文提出了强偶合系统的弱偶合方法处理。利用么正变换,把强偶合系统的哈密顿变成弱偶合系统哈密顿的形式,射频脉冲也作相同的变换,这样强偶合系统的多脉冲实验就能在弱偶合空间{φ}中计算。以AB体系的COSY和2D-J谱为例作了计算和讨论。     

Tunable properties of graphene oxide reduced by laser irradiation

The authors present a nano-plasmonic disk resonator with a gap structure using the multi-mode interference effect coupling. The coupling intensity of the multi-mode interference effect coupling is 1.5 times greater than that of the conventional side coupling. The multi-mode interference effect is adopted as the coupling between the input bus waveguide and the nano-plasmonic disk resonator. The thickness of the dielectric layer, the width of the bus waveguide, and the length of the coupling portion are designed by theoretical calculations.     

Highly efficient optical coupling and transport phenomena in chains of dielectric microspheres

Using the generalized multiparticle Mie theory, we investigate optical coupling and transport through chains of dielectric microspheres. We identify two distinct coupling mechanisms of optical transport in terms of the coupling efficiency between neighboring microspheres, namely, evanescent coupling and nanojet coupling. We demonstrate that perfect whispering gallery mode propagation through a chain of evanescently coupled microspheres can be achieved. However, optical coupling and transport through a chain of nanojet-inducing microspheres is less efficient due to the radiative nature of photonic nanojets. Understanding these two optical coupling mechanisms is critical for selecting appropriate microspheres to build coupled resonator optical waveguides and other photon-manipulation devices for effective and low-loss guiding of photons.     

BEPC同步辐射专用模式横向耦合测量及补偿

对北京正负电子对撞机(BEPC)同步辐射专用模式下的横向二阶差共振耦合做了研究.应用二阶差共振微扰理论,首先测量了BEPC同步辐射专用模式的耦合系数,然后通过数值分析和程序模拟找出耦合来源,最后通过引入斜四极子,成功地对横向耦合进行了补偿.     

Coherent photonic coupling of semiconductor quantum dots

We report a new type of coupling between quantum dot excitons mediated by the strong single-photon field in a high-finesse micropillar cavity. Coherent exciton coupling is observed for two dots with energy differences of the order of the exciton-photon coupling. The coherent coupling mode is characterized by an anticrossing with a particularly large line splitting of 250 microeV. Because of the different dispersion relations with temperature, the simultaneous photonic coupling of quantum dot excitons can be easily distinguished from cases of sequential strong coupling of two quantum dots.