光注入和光电反馈联合作用下垂直腔表面 发射激光器的动力学特性研究

基于自旋反转模型, 研究了垂直腔表面发射激光器(VCSEL) 在光注入和光电反馈共同作用下的动力学特性. 研究结果表明: 一个受到主VCSEL光注入的副VCSEL, 在同时存在光电正反馈时, 其输出的两个线偏振模式(X和Y偏振模) 可呈现周期、 倍周期、 多周期、 混沌等丰富的动力学状态, 且两偏振模动力学态的演化路径存在差异. 各动力学状态在由反馈强度f与注入强度η 所构成的参数空间的分布区域随着主、 副VCSEL 的频率失谐Δν(Δν=ν_m-ν_s, ν_m, ν_s 分别为主、 副VCSEL自由运行时的振荡频率) 的变化而发生改变. 当Δν为正失谐时, 呈现混沌的区域相比零失谐和负失谐时有明显的扩展, 即副VCSEL能在更大的参数范围内实现混沌输出. 对于特定的频率失谐, 分析了光电正反馈强度f和光注入强度η对混沌输出带宽的影响. 通过合理选择反馈强度以及注入强度, 可使副VCSEL混沌输出带宽显著增加.     

Dynamics of Optical Bistability with Kerr-nonlinear Blackbody Radiation Reservoir

In this paper we investigate the nonlinear dynamics for optical bistabile(OB) model of homogeneously broadened two-level atomic medium interacting with a single mode of the ring cavity in the presence of a Kerr-nonlinear blackbody(KNB) radiation reservoir. We show the impact of the relative temperature of the reservoir on the transition between the dynamical states via bifurcation diagrams that represents the relation between maximum values of the output field and the relative temperature for fixed input field. Specifically, decreasing the relative temperature(T_b)causes the system to bifurcate from periodic to chaotic behavior and in turn reverts back to periodic behavior with further decrease of T_b. Varying atomic detuning leads to a change in the nature of the dynamic transition between the system's states from self pulsing to chaotic behavior.     

主副垂直腔面发射激光器动力学系统混沌输出的时延特征及带宽分析

基于垂直腔面发射激光器(VCSEL)的自旋反转模型, 数值研究了由一个光反馈VCSEL (定义为主VCSEL, M-VCSEL)输出的混沌光单向注入到另一个VCSEL (定义为副VCSLE, S-VCSEL)所构成的主副VCSELs系统的混沌动力学特性, 分析了注入强度、M-VCSEL与S-VCSEL之间的频率失谐以及M-VCSEL所受到的光反馈强度对系统混沌输出时延特征(包括强度时延特征(I-TDS) 和相位时延特征(P-TDS))以及输出带宽(BW)的影响. 结果显示: 通过调节注入强度和频率失谐, 该系统混沌输出的两个偏振分量(X-PC和Y-PC)的P-TDS和I-TDS可以同时得到抑制; 进一步分析注入强度和频率失谐对混沌BW的影响, 发现在较大负频率失谐区域, 系统可输出BW超过30 GHz 的X-PC和Y-PC混沌信号; 结合系统混沌输出信号的TDS与BW在注入强度和频率失谐参量空间下的演化特性, 可确定宽带宽、低时延特征混沌信号输出的参量空间区域. 此外, 通过合理调节M-VCSEL 所受到的光反馈强度, 可以显著优化系统的混沌输出信号质量.     

Bifurcation and locking in an multi-quantum-well laser subjected to external injection

Bifurcation and dynamic stability as well as locking in an external light injection multi-quantum-well (MQW) laser are studied. Different dynamic regimes in locking diagram are analyzed with the injection level and frequency detuning. Bifurcate behavior is numerically simulated via the external injection light intensity, frequency detuning, current, linewidth enhance factor, photon loss rate and carrier loss rate, respectively. And the route to chaos from bifurcation, period-doubling and quasi-period are described by numerical analysis. A perturbation equation of four-dimension model and the bifurcation condition are demonstrated. Dynamic stability of the laser is theoretically and numerically analyzed. The bifurcate expression is theoretically given while the maximum locking frequency domain is given. The variational characteristic of the oscillation frequency in the self-pulse regimes versus the injection and detuning are numerically analyzed to find that the relaxation frequency is reduced with adding the detuning in the smaller detuning or with adding the injection in the smaller injection while the relaxation frequency will be increased with adding the detuning in the larger detuning or with adding the injection in the larger injection. We find also that the chaotic spectra are broadened with adding the detuning or narrowed with adding the injection or the current.     

基于双光注入锁定1550 nm垂直腔表面发射半导体激光器产生可调谐毫米波

基于自旋反转模型, 对双光注入下1550 nm 垂直腔表面发射半导体激光器(1550 nm-VCSEL)的非线性动力学行为进行了理论分析和数值仿真研究. 结果表明: 当一个中心波长位于1550 nm 的副VCSEL(S-VCSEL)同时受到来自两个主VCSELs (M-VCSELs)的光注入时, 在适当的注入条件下, S-VCSEL可处于双光注入锁定态. 此时, S-VCSEL中的两偏振模式均呈现频率为两注入光频率之差的周期性振荡, 输出的光谱仅包含两个主频率部分, 即光谱具有单边带特征. 因此, 基于双光注入下S-VCSEL的周期性振荡可以获得两个相互正交的光毫米波. 通过调节两个M-VCSELs之间的频率差异可使毫米波频率在较大范围内连续可调, 通过调节系统参量可以控制毫米波功率以及调制深度. 关键词： 垂直腔表面发射激光器 双光注入 毫米波 调制深度     

Reconfigurable dynamic all-optical chaotic logic operations in an optically injected VCSEL

In a chaotic system of vertical cavity surface emitting laser(VCSEL) with external optical-injection, we propose a novel implementation scheme for reconfigurable dynamic all-optical chaotic logic operations(AOCLOs). Under different key parameters, such as the bias current, the injection strength and the frequency detuning of the injected light field and the VCSEL, we also explore the evolutions of the polarization-bistability with the amplitude of the injected light field when the output of VCSEL is chaotic wave. According to the dynamic evolutions, we find out the optimal value of the frequency detuning that is considered as a control logic signal, and further implement different AOCLOs, such as AND, NAND, OR,NOR, XOR, and XNOR, by controlling the logic operation of the control logic signal between two logic inputs. Moreover,the ability to reconstruct these logic operations is demonstrated under relatively low noise strength of the spontaneous emission.     

平坦宽带混沌激光的产生及同步

利用光纤环长外腔光反馈半导体激光器产生了频谱平坦的宽带混沌激光,其对应的激光频谱可有效地隐藏外腔的谐振频率,增加了系统的保密性.通过单向耦合方式,将产生的混沌激光注入到另一个参数相近的半导体激光器中,实现了平坦宽带混沌同步输出,两同步激光器输出的相关系数达到084.同时实验研究了注入强度和主从激光器的频率失谐对同步质量的影响,结果表明在强光注入锁定下,在很大频率失谐范围内均可实现同步,而且注入强度越大,主从激光器输出的相关系数越大,维持混沌同步所允许的频率失谐范围越大. 关键词： 混沌同步 单向光纤环 光反馈 半导体激光器     

Instability control in microwave-frequency microplasma

This paper introduces comprehensive large-signal analyses of modulation dynamics and noise of a chaotic semiconductor laser. The chaos is induced by operating the laser under optical feedback (OFB). Control of the chaotic dynamics and possibility of suppressing the associated noise by sinusoidal modulation are investigated. The studies are based on numerical solutions of a time-delay rate equation model. The deterministic modulation dynamics of the laser are classified into seven regular and irregular dynamic types. Variations of chaotic dynamics and noise with sinusoidal modulation are examined in both time and frequency domains over wide ranges of the modulation depth and frequency. The results showed that chaotic dynamics can be converted into five distinct dynamic types; namely, continuous periodic signal (CPS), continuous periodic signal with relaxation oscillations (CPSRO), periodic pulse (PP), periodic pulse with relaxation oscillations (PPRO) and periodic pulse with period doubling (PPPD). The relative intensity noise (RIN) of these types is characterized when the modulation frequencies are much lower, comparable to, and higher than the resonance frequency. Suppression of RIN to a level 8 dB/Hz higher than the quantum limit was predicted under the CPS type when the modulation frequency is 0.9 times the resonance frequency and the modulation depth is 0.14.     

Photonic ultrawideband signal generator using an optically injected chaotic semiconductor laser

We propose and demonstrate a method to generate ultrawideband (UWB) signals in the optical domain based on the chaotic dynamics of an optically injected semiconductor laser with optical feedback. The chaotic-UWB pulses with a fractional bandwidth of 116% and central frequency of 6.88?GHz are experimentally generated by controlling the injection strength and frequency detuning of the chaotic laser. The spectrum of the UWB signals is in full compliance with the Federal Communications Commission spectral mask, and the experimental results are qualitatively consistent with the simulated results.     

太赫兹场和倾斜磁场对超晶格电子动力学特性调控规律研究

微带超晶格在磁场和太赫兹场调控下表现出丰富而复杂的动力学行为, 研究微带电子在外场作用下的输运性质对于太赫兹器件设计与研制具有重要意义. 本文采用准经典的运动方程描述了超晶格微带电子在沿超晶格生长方向(z方向)的THz场和相对于z轴倾斜的磁场共同作用下的非线性动力学特性. 研究表明, 在太赫兹场和倾斜磁场共同作用下, 超晶格微带电子随时间的演化表现出周期和混沌等新奇的运动状态. 采用庞加莱分支图详细研究了微带电子在磁场和太赫兹场调控下的运动规律, 给出了电子运行于周期和混沌运动状态的参数区间. 在电场和磁场作用下, 微带电子将产生布洛赫振荡和回旋振荡, 形成复杂的协同耦合振荡. 太赫兹场与这些协同振荡模式之间的相互作用是导致电子表现出周期态、混沌态以及倍周期分叉等现象的主要原因.     

光注入提高半导体激光器混沌载波发射机的带宽

外光反馈下的半导体激光器可视为混沌载波发射机.数值研究发现，外部强光注入可以显著提高混沌载波发射机的带宽，带宽提高的程度在一定范围内与注入光的强度成正比.当外部光注入系数k_inj=0.39时，混沌载波的带宽由无光注入时的2.7GHz增大到14.5GHz，提高了5倍多.研究还发现，在相同的注入强度条件下，当注入光的频率比半导体激光器的中心频率高2—4GHz时，可实现最大限度的带宽增强.此外，适当提高半导体激光器的偏置电流也可以在一定程度上提高其产生的混沌载波的带宽. 关键词： 半导体激光器 混沌 带宽     

Bifurcation magnetic resonance in type (100) films upon in-plane magnetization

The magnetization dynamics in (100) single-crystal films with a cubic anisotropy has been studied by numerical simulation. It has been shown that the additional (bifurcation) resonance caused by the bistability, i.e., two closely spaced equilibrium magnetization states, appears upon in-plane magnetization along the hard axis. The change in the resonance region and the corresponding dynamic regimes with a variation in the RF field or with a small detuning of the magnetizing field has been investigated. The regular and chaotic precession regimes near the bifurcation resonance have been revealed. The states of dynamic bistability have been found.     

Numerical study of the spiking instability caused by modulation frequency detuning in an actively mode-locked solid-state laser

We have studied both analytically and numerically the transient active mode locking in the case of a modulation frequency detuning. Analytical results for pulse width and position, extending previous works, are obtained within the frame of the stationary theory by assuming that a short pulse restores its shape after each round trip. Numerical evaluation leads to relaxation oscillations and change of the short-pulse shape. The results of both approaches agree with each other only for small detunings, when laser is operated in the steady state. For larger detunings the laser dynamics change dramatically, and the three operation modes observed earlier in experiments were demonstrated numerically: sequences of damped relaxation oscillations, deep periodic spiking and chaotic spiking. The periodic spiking can be used to increase the intensity of mode-locked pulses.     

用半导体环形激光器产生混沌信号

提出了一种由一个分布式反馈激光器为主激光器和一个半导体环形激光器为从激光器组成的主从式激光混沌系统方案,主激光器产生的光单向注入到从激光器中,通过调整注入系数、主从激光器的失谐频率和从激光器的偏置电流,使从激光器工作在混沌状态,输出混沌信号。从基于光注入条件下的环形激光器的速率方程组入手,数值模拟了主从激光器的失谐频率、注入系数和从激光器的偏置电流3个工作参量对从激光器输出动态的影响。研究表明:外光注入条件下,半导体环形激光器可以产生混沌信号。通过分析得出:当失谐频率为3.9 GHz、注入系数为0.07、偏置电流为81 mA时,环形激光器可以产生功率谱平坦、带宽较宽的高质量混沌信号。     

CSNS-II超导椭球腔失谐研究

中国散裂中子源二期束流功率升级到500 kW，直线加速器H-的能量增益由现在的80 MeV提高到300 MeV以上，其中150 ~ 300 MeV能量段采用648 MHz β_g=0.60的5-cell超导椭球腔结构。超导椭球腔具有加速梯度高、结构简单、后处理容易等优点，缺点是结构强度弱、易失谐。本文主要研究该椭球腔的失谐特性。利用COMSOL Multiphysics软件进行了计算分析，在两端固定边界条件下，裸腔的氦压敏感性系数K_P=–45.705 Hz/mbar(1 mbar=100 Pa)，洛伦兹力失谐因子K_L=1.574 Hz/(MV/m)2。增加加强环并优化其位置来改善氦压敏感性系数和洛伦兹力失谐因子，通过计算分析最终确定选择双加强环方案来减小椭球腔的失谐。两个加强环位置分别取在75和120 mm的位置，腔体失谐的改善最大，K_P=6 Hz/mbar，K_L=0.43 Hz/(MV/m)2。为了更准确地计算椭球腔的氦压敏感性系数和洛伦兹力失谐因子，本文引入调谐刚度边界条件进行失谐分析，在椭球腔调谐器端设置30 kN/mm边界条件，另一端固定，计算得到氦压敏感性系数为4.8 Hz/mbar，洛伦兹力失谐因子1.99 Hz/(MV/m)2，满足工程要求。另外，用CST软件对椭球腔的动态洛伦兹力失谐进行了初步分析，用软件Workbench计算了椭球腔的振动本征频率，结果显示，振动本征频率离射频脉冲重复频率及环境振动频率较远，不易发生共振失谐。     

Power-induced polarization switching and bistability characteristics in 1550-nm VCSELs subjected to orthogonal optical injection

The polarization switching(PS) and polarization bistability(PB) characteristics of a 1550-nm vertical-cavity surfaceemitting laser(VCSEL) subjected to orthogonal optical injection are systematically investigated.The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power.The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS.In the case of forward scanning injected power,with the increase of frequency detuning level between the VCSEL and the injected light,the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning.In the case of reversely scanning injected power,the injected power required for PS displays fluctuant changes within the whole frequency detuning range.Specifically,PS may disappear under certain negative frequency detuning and large bias current.Furthermore,the hysteresis width as a function of the frequency detuning is calculated,and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning.     

短外腔偏振旋转光反馈下1550nm垂直腔面发射激光器的动力学特性研究

基于扩展的自旋反转模型,对短外腔偏振旋转光反馈下1550 nm垂直腔面发射激光器的动力学特性进行了数值仿真和理论分析.研究结果表明:增加反馈强度会导致多个偏振开关现象出现,中等反馈强度下呈现丰富的动力学状态,譬如单周期、倍周期、准周期及混沌态,增加注入电流使Y方向线偏振模的工作区域被压缩;随着反馈延迟时间的增加,在弱光反馈时,偏振模跳变现象将会以特定的频率发生,施加中等的反馈强度将会导致模式跳变的频率增加,并且出现各种新的动力学状态,包括拍频单周期、拍频脉冲包络、拍频准周期和拍频混沌态.新动力学行为的出现是由于短外腔区激光器的动力学特性对相位变化非常敏感,从而使外腔模式间的拍频效应发挥了关键作用.此外还发现各种动力学状态之间会伴随模式间的跳变而发生相互跳变.     

Experimental Investigation of Chaos Synchronization in DFB Diode Lasers with Unsymmetrical Scheme

We experimentally generate high dimension chaotic waveforms with smooth spectrum using a distributed feedback （DFB） semiconductor laser with unidirectional fibre ring long-cavity feedback, and implement the stable chaos synchronization when the chaotic light is injected into a solitary DFB laser diode. The synchronization quality is investigated by time-domain and frequency-domain analysis separately, The frequency-domain analysis indicates that the synchronization has higher quality in the high frequency band. The influences of the injection strength and the frequency detuning on the synchronization are measured. Our experimental results show that the robust synchronization can be maintained with the optical frequency detuning from -11GHz to 40 GHz.     

耦合不连续系统同步转换过程中的多吸引子共存

本文研究了耦合不连续系统的同步转换过程中的动力学行为, 发现由混沌非同步到混沌同步的转换过程中特殊的多吸引子共存现象. 通过计算耦合不连续系统的同步序参量和最大李雅普诺夫指数随耦合强度的变化, 发现了较复杂的同步转换过程: 临界耦合强度之后出现周期非同步态(周期性窗口); 分析了系统周期态的迭代轨道,发现其具有两类不同的迭代轨道: 对称周期轨道和非对称周期轨道, 这两类周期吸引子和同步吸引子同时存在, 系统表现出对初值敏感的多吸引子共存现象. 分析表明, 耦合不连续系统中的周期轨道是由于局部动力学的不连续特性和耦合动力学相互作用的结果. 最后, 对耦合不连续系统的同步转换过程进行了详细的分析, 结果表明其同步呈现出较复杂的转换过程.     

非共振激发条件下微腔中激子自发辐射的时间分辨光谱

低温下,测量了InGaAs量子阱平面微腔的时间分辨光谱。在非共振激发条件下,观察到上下两支腔极化激元光荧光的衰退时间与失谐无关;下支腔极化激元光荧光的上升时间也与失谐无关;而上支腔极化激元光荧光的上升时间却与失谐有强烈的依赖关系,随着从负失谐到正失谐的增加,上升时间逐渐减小。对实验结果的物理根源进行了讨论。