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.     

Nonlinear optical interfaces: Switching behavior

We report the results of a study of the switching behavior of the interface between an ordinary dielectric and a nonlinear dielectric material with an intensity-dependent index of refraction. The non-linear dielectric used for these experiments consisted of a liquid suspension of dielectric particles. Because this medium has a very large effective nonlinearity, it was possible to perform these experiments with the CW output of an argon ion laser. Our experimental results are in excellent agreement with the predictions of numerical calculations based on a two-dimensional Gaussian input beam. We also report the observation of an unstable reflectivity state with a lifetimesim 10^{3}times the response time of the nonlinear medium.     

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.     

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。     

新型数控开关稳压电源设计

根据当前高频开关电源的现状和进展。采用现今应用广泛的PWM控制来满足DC-DC变换的要求;研制出一台BOOST型拓扑方式的DC—DC开关电源实验样机。针对高频率下开关电源产生的开关损耗,选择合适的方案和设计缓冲电路、高频率下功率器件驱动,并在设计中采用模块化的设计方法,通过理论估算、软件仿真、实验等环节进行数控开关稳压电源硬件电路的设计和制作。     

扰动法非线性晶体生长过程数值模拟研究

采用扰动法对使用Cz(Czochralski)法非线性晶体生长过程中提拉速度和熔液平均温度场进行了数值模拟研究,实验结果可用于实现晶体等径生长中提拉速度和熔液平均温度的预测控制。研究表明,熔液平均温度(提拉速度)不变时,提拉速度(熔液平均温度)随环境毕奥数的增加和/或熔液毕奥数的减小而增大。进一步研究,熔液若不会组分过冷,可以得到提拉速度的最大值,并在整个生长过程中,必须控制提拉速度小于它的临界上限,否则晶体生长过程将失败。     

高非线性微结构光纤环镜开关效应的实验研究

利用基于高非线性微结构光纤的非线性光纤环镜,在10Gb/s光传输系统中进行了全光开关的实验研究.利用中心波长在1550nm的皮秒脉冲激光器,在以25m长微结构光纤作为非线性介质构成的光环镜中,实现了非线性相移为π的开关操作,同时还发现这种全光开关具有脉冲整形的功能.     

Switching Characteristics of Nonlinear Field-Effect Transistors: Gallium-Arsenide Versus Silicon

A study of the switching properties of GaAs FET's and other nonlinear elements whose high field velocity saturates without negative differential mobility demonstrates that the high-bias swiching times of GaAs are determined by velocity saturation. Silicon switches are also studied, and situations where GaAs and Si switching properties may be similar are discussed.     

ECLD激光器三种模型的双稳特性比较

为了研究频率偏离增益峰值时光栅外腔半导体激光器的双稳特性,对比了以前研究双稳态的原简化模型和近期建立的H参量简化模型、H参量模型所得的双稳环环宽及其存在的条件;采用数值计算和模拟的方法,讨论了三种模型在不同剩余反射率下的双稳环环宽与频率的关系,将H参量简化模型、H参量模型在相同模式中环宽随剩余反射率的变化曲线进行了比较.结果表明,三种模型在增益峰值处的双稳特性相同,第一种模型只能反映增益峰值处的双稳特性,后两种模型能够展示调谐范围内的双稳特性,但在增益峰值两侧新的两种模型的双稳特性有很大的差异,所以在研究ECLD的双稳特性时考虑双稳环随H参量的变化而倾斜十分必要.