Low-frequency fluctuation in multimode semiconductor laser subject to optical feedback

Dynamics of a semiconductor laser subject to moderate optical feedback operating in the low-frequency fluctuation regime is numerically investigated.Multimode Lang-Kobayashi(LK)equations show that the low-frequency intensity dropout including the total intensity and sub-modes intensity is accompanied by sudden dropout simultaneously,which is in good agreement with experimental observation.The power fluctuation is quite annoying in practical applications,therefore it becomes important to study the mechanism of power fluctuation.It is also shown that many factors,such as spontaneous emission noise and feedback parameter,may influence power fluctuation larger than previously expected.     

Current-driven state-bistability and power-bistability in a DFB semiconductor laser subject to optical injection

In this paper, current-driven state-bistability and power-bistability in a distributed feedback (DFB) semiconductor laser (LD) subject to external optical injection have been investigated experimentally. The results show that, by sweeping the bias current of slave LD along different routes nearby the threshold, both the power-bistability and the state-bistability between locking and bimodal regime can be observed under the suitable injection power, but these bistable phenomena will disappear under much large injection power. Additionally, the dependence of the width of the state-bistablility loop on the injection power has been discussed.     

Low frequency fluctuations in a multimode semiconductor laser with optical feedback

We study a multimode semiconductor laser subject to a moderate optical feedback. The steady state is destabilized by either a simple Hopf bifurcation leading to in phase dynamics or by a degenerate Hopf bifurcation leading to antiphase dynamics. The degenerate bifurcation is also a source of multiple coexisting attractors. We show that a simple interpretation of the low frequency fluctuations in the multimode regime is provided by a chaotic itinerancy among the many coexisting unstable attractors produced by the degenerate Hopf bifurcation.     

Speckle-pattern contrast of semiconductor laser propagating in a multimode optical fiber

Speckle patterns produced by coherent light from a GaA1As double-hetero-structure laser diode that has been transmitted through a multi-mode optical fiber are experimentally studied by analyzing the average contrast. It has been found that the speckle contrast observed in the far-field region is significantly lowered when the spectral width of a laser diode is as broad as a few tens of Angstroms.     

Mode structure of a semiconductor laser subject to filtered optical feedback

We present an analytical study of the mode structure of a semiconductor laser subject to filtered optical feedback (FOF). First, we derive expressions for the solution sets that define the structure of the modes. We then employ continuation techniques to investigate how this structure changes as filter width, filter detuning and feedback phase are varied. This leads to a comprehensive picture of the FOF laser’s mode structure. In particular, we find an equation for the boundary of the parameter region in which one finds two separate components of modes.     

Multipulse excitability in a semiconductor laser with optical injection

An optically injected semiconductor laser can produce excitable multipulses. Homoclinic bifurcation curves confine experimentally accessible regions in parameter space where the laser emits a certain number of pulses after being triggered from its steady state by a single perturbation. This phenomenon is organized by a generic codimension-two homoclinic bifurcation and should also be observable in other systems.     

Excitability in a quantum dot semiconductor laser with optical injection

We experimentally analyze the dynamics of a quantum dot semiconductor laser operating under optical injection. We observe the appearance of single- and double-pulse excitability at one boundary of the locking region. Theoretical considerations show that these pulses are related to a saddle-node bifurcation on a limit cycle as in the Adler equation. The double pulses are related to a period-doubling bifurcation and occur on the same homoclinic curve as the single pulses.     

外光注入半导体激光器实现时钟分频

从理论和实验上研究了利用光注入半导体激光器对高重复速率光脉冲产生的周期振荡和时钟分频现象.结果表明，光注入半导体激光器引起的二倍周期振荡是使注入脉冲重复频率分频的直接原因.通过耦合速率方程，数值模拟了半导体激光器在外光注入时输出光的时间序列和功率谱，并且分析了激光腔内各种周期振荡的特征.研究表明，当注入光使半导体激光器出现稳定的二倍周期振荡，且注入光的重复频率为此振荡频率的二倍时，时钟分频即可产生实验中，采用重复频率为6.32GHz的光脉冲注入Fabry-Perot激光器，实现了3.16GHz时钟分频信号 关键词： 周期振荡 时钟分频 光谱侧带 光注入     

Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.     

Chaos generation in a semiconductor ring laser with an optical injection

Two chaos generation schemes are demonstrated numerically based on a semiconductor ring laser (SRL) with either a constant or a chaotic optical injection from an external distributed feedback (DFB) laser. Under a certain bias current, the chaotic output can be generated by the SRL with appropriate injection parameters. Parameter map is achieved numerically to show types of oscillation in the SRL. Bifurcation diagrams and Lyapunov exponent spectra roughly describe the routes to chaos for the SRL with disturbance. A bandwidth-enhanced chaos generation can be describes based on the chaotic optical injection scheme. The bandwidth of the bandwidth-enhanced chaos generated is about 12 GHz, which achieves approximately a two-fold increase compared with the constant injection scheme.     

Periodic oscillation within the chaotic region in a semiconductor laser subjected to external optical injection

We report on the experimental observation of periodic windows within the chaos of the output of a semiconductor laser that is subjected to external optical injection. Continuously sampled spectra of the slave-laser output as the injection level is increased reveal the general behavior of the system as well as features that suggest that the periodic oscillation forms a distinct island within the chaotic region in the parameter space.     

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。     

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。     

Antiphase dynamics of a multimode quantum well semiconductor laser

A novel multilongitudinal mode model of a semiconductor laser is presented. The model takes into account four-wave mixing of the longitudinal modes and is based on the correct procedure of simultaneous expansion of the population inversion in time and space series. It is shown that the model has antiphase regimes similar to those observed in experiment. Such behavior exists in a narrow range of the carrier diffusion coefficient, which allows us to estimate the value of this parameter.     

外光注入半导体激光器实现重复速率可调全光时钟分频

采用Fabry-Perot半导体激光器作为全光时钟分频器件,利用光注入半导体激光器产生的非线性动力学特性,实现了光脉冲的重复速率在9.0 GHz到19.8 GHz范围内连续可调的全光时钟分频. 同时利用半导体激光器速率方程,对脉冲光注入半导体激光器产生时钟分频进行了数值模拟. 实验和模拟结果表明半导体激光器在光注入的驱动下处于一周期振荡状态,当一周期振荡的二次谐波频率接近脉冲光的重复速率时,其二次谐波和基频被脉冲光同时锁定,此时将输出频率为脉冲光重复速率一半的时钟信号. 同时研究了波长失谐量和注入光功率对 关键词： 周期振荡 时钟分频 光注入 非线性动力学     

Bifurcations and chaos in a semiconductor laser with coherent or noisy optical injection

This paper investigates theoretically the dynamical sensitivity of semiconductor lasers to external optical signals. Bifurcation analysis of ordinary rate equations, describing noise-free lasers with pure coherent external signal, reveals that considerable modifications to the extend and type of externally induced bifurcations and chaos are possible by tailoring of the laser active-medium and resonator configurations. Extending the analysis to stochastic rate equations, which describe lasers with spontaneous emission noise and noisy external signal, reveals further dynamical effects owing to the introduced random fluctuations. In particular, phase-fluctuations (incoherence) in the external signal can have a dramatic impact on induced bifurcations and chaos. The observed strong sensitivity of laser instabilities to the intensity and coherence of external signal can provide a very sensitive means to detect ultra low levels of laser radiation.     

Observation of optical bistability in a GaAlAs semiconductor laser under intermodal injection locking

Experimental observation of optical bistability in a semiconductor laser under intermodal injection locking is reported for what is believed to be the first time. It is seen that a change in injection power of several microwatts or master laser frequency detuning of a few hundred megahertz can induce a change of as much as several hundred gigahertz in the lasing frequency of the slave laser. The results are in qualitative agreement with theoretical predictions.     

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.     

Secure communication scheme using chaotic laser diodes subject to incoherent optical feedback and incoherent optical injection

We propose a secure communication scheme based on anticipating synchronization of two chaotic laser diodes, one subject to incoherent optical feedback and the other to incoherent optical injection. This scheme does not require fine tuning of the optical frequencies of both lasers as is the case for other schemes based on chaotic laser diodes subject to coherent optical feedback and injection. Our secure communication scheme is therefore attractive for experimental investigation.