光孤子双稳态及其开关特性

本文介绍了光孤子双稳态的概念和近年来对一维光孤子双稳态及其开关特性的研究进展情况。     

切趾型非线性布拉格光纤光栅双稳开关及动态特性的理论研究

基于耦合模方程,利用含有时间推移变量的传输矩阵方法对非线性布拉格光栅(NLBG)双稳特性进行了理论分析,结果表明:在稳态情况下,不同切趾参数对NLBG双稳开关的阈值影响不同,并且正负切趾具有明显的光隔离器特点。考虑连续波输入,NLBG表现出的双稳开关特性在动态情形下极易出现一定周期性的自脉动,而且当输入光强增大到临界光强,输出可由自脉动转变为混沌状态;考虑切趾参数一定时,耦合系数的增大会导致脉动基座宽度和频率减小,当耦合系数达到一定数值后,输出状态将转变为弛豫衰减振荡。     

超短光脉冲在有源三芯非线性光纤耦合器中开关和传输特性的数值分析

基于耦合非线性薛定谔方程(CNLSEs),利用分裂步长傅里叶方法(SSFM),研究了超短光脉冲在有源三芯非线性光纤耦合器中的传输和开关特性.重点分析了在一阶色散耦合系数和二阶色散耦合系数的影响下,线性增益系数和有限增益带宽对脉冲传输和开关特性的影响.研究表明,线性增益系数能增大开关陡峭性、降低开关临界能量、提高开关效率;虽然有限增益带宽使耦合器开关特性变差,但是它不仅能显著抑制由线性增益系数引起的脉冲压缩和放大,而且还能有效抑制由一阶色散耦合系数引起的脉冲展宽和分离以及由二阶色散耦合系数引起脉冲高频振荡,使光脉冲在三纤芯间呈现出类似无源光纤耦合器那样的周期性耦合传输特性.     

具有高阶耦合色散系数双芯非线性光纤耦合器开关的数值分析

基于耦合非线性薛定谔方程(NLSE),利用分裂步长傅里叶方法(SSFM),研究了具有高阶耦合色散系数时,双芯非线性光纤耦合器中的传输和开关特性.模型中,一阶耦合色散系数的存在类似于群速度失配,二阶耦合色散系数类似于群速度色散,并且会对另一个纤芯中的信号产生线性互调制.研究表明当一阶耦合色散系数较小时,光脉冲仍能在二纤芯之间周期性耦合传输,并且表现出良好的开关特性,当一阶耦合色散系数增大时,脉冲耦合传输的周期性和陡峭的开关特性遭到破坏,光脉冲在传输中发生分裂;二阶耦合色散系数使耦合器的耦合长度减短,开关阈值功率增加,开关特性也变得更加陡峭.     

Switching Dynamics of a Post-Aligned Bistable Nematic Liquid Crystal Device

The operation of a post-aligned bistable nematic (PABN) liquid crystal device is simulated using a dynamic finite-element implementation of the Landau–de Gennes theory in 3D. Two topologically distinct stable director profiles of higher and lower tilt angles are identified. The switching process between these two states is simulated while monitoring the variation in total free energy of the liquid crystal material. Maxima in the free energy, acting as energy barriers separating the two stable states, are shown to coincide with the formation of $-1/ 2$ defect lines in the director field.      

双稳系统中非周期随机共振的数值仿真

本文采用互相关方法研究了噪声和随机二进制信号同时激励双稳系统(施密特触发器和双势阱系统)时的输出响应，观察到非周期随机共振：利用双稳系统中的非周期随机共振效应，可以减小随机信号传输中的噪声水平，改善输出信号质量，这在数字通信领域具有十分重要的意义。     

All-Optical Label Swapping Using Bistable Semiconductor Ring Laser in an Optical Switching Node

This paper demonstrates an optical node that simultaneous carries out multicast optical switching and all-optical label swapping. While the optical payload is being forwarded by a fast optical switch matrix, the optical label is processed by a semiconductor ring laser (SRL) bistable. Old address bits in the label are erased by optically blocking the switching of the ring laser and new address bits are inserted by modulating the output from SRL directly. This label swapping scheme is the first demonstration of bit-level data processing using the all-optical logic capabilities of a semiconductor ring laser.     

Stabilization of Discrete-Time Nonlinear Switching Systems

This paper presents sufficient conditions for the stabilization of saturated switching nonlinear discrete- time systems. The type of nonlinearity is the so-called Lur’e type. Less conservative stability regions are obtained. This fact is shown upon a numerical example.     

Processing and Low Voltage Switching of Organic Ferroelectric Phase‐Separated Bistable Diodes

The processing of solution‐based binary blends of the ferroelectric random copolymer poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE) and the semiconducting polymer poly(9,9‐dioctylfluorenyl‐2,7‐diyl) (PFO) applied by spin‐coating and wire‐bar coating is investigated. By systematic variation of blend composition, solvent, and deposition temperature it is shown that much smoother blend films can be obtained than reported thus far. At a low PFO:P(VDF‐TrFE) ratio the blend film consists of disk‐shaped PFO domains embedded in a P(VDF‐TrFE) matrix, while an inverted structure is obtained in case the P(VDF‐TrFE) is the minority component. The microstructure of the phase separated blend films is self‐affine. From this observation and from the domain size distribution it is concluded that the phase separation occurs via spinodal decomposition, irrespectively of blend ratio. This is explained by the strong incompatibility of the two polymers expressed by the binary phase diagram, as constructed from thermal analysis data. Time resolved numerical simulation of the microstructure evolution during de‐mixing qualitatively shows how an elevated deposition temperature has a smoothening effect as a result of the reduction of the repulsion between the blend components. The small roughness allowed the realization of bistable rectifying diodes that switch at low voltages with a yield of 100%. This indicates that memory characteristics can be tailored from the outset while processing parameters can be adjusted according to the phase behavior of the active components.     

非对称非线性定向耦合器开关特性研究

利用拉格朗日变分法原理,分析了非对称非线性定向耦合器的开关特性.研究表明:增大第一纤芯的相速度能够降 低开关的阈值功率,但开关的陡峭性变差,且当相位失配量增大到一定程度,输入低功率脉冲时,光脉冲的部分能量将一直保 持在直通纤芯臂内不能耦合到第二纤芯.增大第一纤芯的有效模场面积将导致开关的阈值增大.同时,当两纤芯都为反常...     

Bragg光纤光栅的非线性开关特性研究

从耦合模理论出发,通过单独改变入射波中心波长、光纤光栅长度及耦合系数,数值研究了光纤光栅双稳态开关特性,给出了输入输出特性与这些参数的单一依赖关系曲线,得出一些有意义的结论.在此基础上,对如何减小非线性开关阈值进行了总结和探讨,并提出运用稀土掺杂光纤光栅与F-P腔相结合的结构来降低光开关阈值.     

对非线性二波导耦合器光开关的分析

本文报道对Ｄｅｅｒｉｎｇ等人最近提出的非线性二波导耦合器光开关的一种新的分析方法,并给出计算结果,这种方法可提供有关相们变化的有用信息,并且可用来处理其它种类的二波导耦合器。     

非线性抛物线势与量子阱双稳态系统的稳定性

基于超晶格量子阱的双稳态效应,在经典力学框架内,把粒子的运动方程化为了具有阻尼项和受迫项的经典Duffing方程.利用Melnikov方法分析了系统的全局分叉与Smale马蹄变换意义上的混沌行为,给出了系统进入混沌的临界条件值.结果表明,只要参数满足临界务件,系统就是"数学"稳定的.考虑到系统进入混沌的临界条件与它的参数有关,只需适当调节这些参数,混沌就可以得以避免或控制,这为光学双稳态器件的制备和稳定工作提供理论依据.

Abstract：

Based on the bistable effect of the superlattice quantum well, the particle motion equation is reduced to the classical Dulling equation in the classical mechanics frame. The chaotic behaviors with the Smale horseshoe are analyzed by Melnikov method. The critical condition approaching to chaos is found. It is shown that the system is stable if the critical condition is satisfied, because the critical condition entered in a chaos is related to the parameters of the system, provided regulating a parameters of the system, the chaos can be avoided or controlled. The theoretical analysis is provided to the design of optical bistable stable cells.     

基于混合观测器的非线性系统的脉冲控制

该文针对基于有限状态自动机的非线性脉冲混合动态系统,设计一种新的脉冲混合观测器,然后应用有限状态自动机理论和Backstepping方法设计了基于混合观测器的脉冲输出反馈控制器,并构造了多Lyapunov函数,通过混合系统的渐近稳定性理论以及多Lyapunov函数法给出整个闭环系统渐近稳定的充分条件,数值仿真验证了该控制器的有效性。     

非线性压电耦合对L型梁俘能器性能的影响

以二自由度的L型梁双稳态压电俘能器为研究对象,研究了非线性压电耦合关系中的一、二次非线性系数对俘能器输出功率和主梁运动的影响。通过对无量纲动力学方程的数值进行了仿真分析,结果表明,当激励幅值较大时,非线性压电耦合对俘能器输出功率和主梁运动有明显的影响;非线性压电耦合系数越大,输出功率越大,而俘能器的振动位移越小。非线性压电耦合的一次非线性系数取正值时,俘能器的响应优于线性耦合时的俘能器响应,取负值,则反之;而无论二次非线性系数取何值,非线性耦合时俘能器的响应都优于线性耦合时俘能器的响应。     

Bistable Interface: Reversible Switching of Rectifying to Nonrectifying Current Across Heterostructured Thin Films of MOFs

A diverse range of physicochemical properties offered by metal-organic frameworks (MOFs) is highly engaging in thin film configurations, specifically for device applications. Heterostructured thin films of MOFs allow to utilize the unique interfaces that develop within such configurations. Typically, interface is monostable and electrical transport across heterostructured MOF thin films has so far been realized to be either Ohmic or rectifying (p-n junction) type. This work reports the emergence of a bistable interface in a heterostructured thin film of Mott-like electrically insulating MOFs whereby rectifying to nonrectifying current can be reversibly switched by applying thermal energy. The inherent resistive switching behavior of both the individual MOF layers at different temperatures coupled with charge-transfer apparently makes the interface complex.     

Numerical Study of Few-Cycle Pulses by Nonlinear Compression in Two-Photon Semiconductor Amplifiers

Optical pulse compression down to a few optical cycles by the ultrabroadband gain of nonlinear two-photon process in semiconductors is proposed. Recent experimental demonstration of semiconductor two-photon gain (TPG) has motivated this analysis of ultrashort pulse dynamics with realistic semiconductor parameters. Comprehensive material model, including TPG, carrier depletion, linear absorption, Kerr effect, plasma response of injected carriers, and the material dispersion were numerically simulated using the finite-difference time-domain method. Pulse compression down to a few optical cycles is theoretically predicted.      

数控开关电源的研究

文章研究一款实验室用小功率数控开关电源,选用半桥型电路作为其主电路,采用DSP作为数控开关电源的控制核心和一种新型数字PID算法,给出了主电路及控制电路的设计方法,利用MATLAB建立了PWM子系统和数字PID控制模型,对所取主电路及控制回路参数进行了仿真。仿真结果表明该系统具有良好的调节功能,既满足一定控制精度要求,又满足实时性要求。     

脉冲噪声中基于指数函数的可变拖尾非线性变换设计

针对脉冲噪声中的信号检测问题,该文提出一种基于指数函数的非线性变换函数设计与优化方法。该方法利用指数函数衰减速度可调的优点,适用于脉冲噪声的各种分布模型。通过引入效能函数,将非线性函数设计问题转化为以效能最大化为目标的阈值与底数参数优化问题。由于效能是关于待优化参数的连续可导且单峰函数,该优化问题可采用数值优化方法如单纯形法快速稳健地求解。性能分析表明,针对脉冲噪声常用的对称α稳定分布、Class A分布和高斯混合分布,该文方法均能取得基本最优检测性能,基于实测大气噪声仿真的通信误码率也明显优于传统的削波器和置零器。因此,该文为各种分布的脉冲噪声提供了一个统一的最优抑制解决方法。

     

光通讯器件中F-P标准具型色散研究

推导了光通信系统中任意两平行光学表面间由多光束干涉引起的群延迟色散(GDD)的表达式;分析了GDD的变化规律,包括周期性、平方律特性和对表面反射率的依赖关系。同时指出通过法布里-珀罗(F-P)光学标准具后的反射波色散特性与透射波色散特性间的差异,对反射波色散中出现的奇异性进行了讨论。