Dependence of the experimental stability diagram of an optically injected semiconductor laser on the laser current

An experimental study of the dynamical properties of a semiconductor laser subjected to external optical injection is presented. The effect of the laser current on the dynamical regions as found in an experiment is reported on for the first time. The nonlinear dynamical regions are mapped in the parameter plane consisting of the detuning between lasers and the injection strength, by utilizing a method of condensing the information in output spectra to two-dimensional images. Corresponding maps for different values of the slave laser current are recorded. The recordings present conclusive experimental evidence that the overall locations of the dynamical regions scale with respect to the relaxation–oscillation frequency and the injection strength relative to the free running laser power. The results further support the theoretical prediction that the linewidth-enhancement factor is the parameter which most strongly affects the dynamics. Locally, specific chaotic regions are found to grow for higher operating points of the slave laser. A complete characterization of the parameters that enter the rate-equations for the visible output AlGaInP laser used in this experiment is performed.     

Effect of the External Mirror Feedback Strength in the Dynamics and Spectrum of the Injected Semiconductor Lasers

We analytically investigate the effect of an external mirror on the stability of an injected semiconductor laser, the latter treated as injected damped oscillators. In the studied configuration, the injected semiconductor laser with an external mirror is under the influence of a chaotic oscillating optical signal that is generated by a similar semiconductor master laser. We derive our results in terms of the damping rate and resonance frequency. We show that the external mirror can eliminate the unstable modes of the injected laser at low frequencies. Furthermore, the mirror can enhance the damping of the oscillation modes of the injected semiconductor laser; consequently, the driven response of the injected laser may have a broad spectrum, even wider than that of the chaotic driving signal. We also show results for the bandwidths of the injection amplitude and phase increment as functions of the injection rate and feedback strength of the external mirror. In addition, we use bifurcation and time-series curves to describe the dynamical behavior of the injected laser. We identify the feedback strength of injected laser, relative to that of the master laser, which induces synchronization between the injected-laser oscillation modes and the master laser.     

半导体激光器混沌输出的延时特征和带宽

外腔延时特征和带宽是影响混沌激光应用的两个重要参量.本文将一个单路光反馈的半导体激光器输出的激光部分地注入到另一个双路滤波光反馈的半导体激光器中,从而构成一个具有外光注入的双路滤波光反馈半导体激光器系统,即主从激光器系统,用于抑制混沌激光的延时特征并研究其带宽.数值研究了外光注入系数、反馈强度、抽运因子和滤波器带宽对系统输出混沌激光的延时特征的影响,然后将该系统对延时特征的抑制效果和具有外光注入的单路光反馈半导体激光器系统、具有外光注入的双路光反馈半导体激光器系统、具有外光注入的单路滤波光反馈半导体激光器系统以及无光注入双路滤波光反馈半导体激光器系统进行对比和分析,结果表明本文提出的方案对延时特征的抑制效果最好.然后在本文提出的具有外光注入的双路滤波光反馈半导体激光器系统中,延时特征被有效抑制的参数条件下研究系统输出混沌激光的带宽,结果表明,通过适当选择参数的取值,本文提出的方案可以提高系统输出混沌激光的带宽.     

基于椭圆偏振光注入垂直腔表面发射激光器的正交偏振模式单周期振荡产生两路光子微波

提出了基于椭圆偏振光注入下垂直腔表面发射激光器(VCSEL)输出的正交偏振模式单周期(P1)振荡来同时获取两路光子微波的实现方案, 并进行了相关仿真研究. 结果表明: 在合适的参数条件下, 一个自由运行的VCSEL(定义为主VCSEL, M-VCSEL)可输出椭圆偏振光, 其X偏振分量和Y 偏振分量具有相同的激射频率; 将M-VCSEL输出的椭圆偏振光注入到另外一个VCSEL(定义为副VCSEL, S-VCSEL), 在给定主副VCSEL间频率失谐的条件下, 通过选择合适的注入强度可使S-VCSEL 中两个偏振分量均呈现单周期(P1)振荡, 从而可获得两正交的光子微波信号; 随着注入强度的增加, 光子微波的频率以及功率均呈现增加的趋势; 结合微波频率、功率以及输出光谱中第一边带和第二边带的幅度差在由注入强度和频率失谐所构成参数空间下的分布图, 可确定获取高品质微波信号的优化注入参数范围.     

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.     

Novel photonic applications of nonlinear semiconductor laser dynamics

With a proper perturbation, even a single-mode semiconductor laser can exhibit highly complex dynamical characteristics ranging from stable, narrow-linewidth oscillation to broadband chaos. In recent years, three approaches to invoke complex nonlinear dynamical states in a single-mode semiconductor laser have been thoroughly studied: optical injection, optical feedback, and optoelectronic feedback. In each case, the nonlinear dynamics of the semiconductor laser depends on five intrinsic laser parameters and three operational parameters. The dynamical state of a given laser can be precisely controlled by properly adjusting the three operational parameters. This ability to control the dynamical behavior of a laser, combined with the understanding of its characteristics, opens up the opportunity for a wide range of novel applications. This paper illustrates the utilization of the rich nonlinear dynamics of single-mode semiconductor lasers by focusing on the period-one oscillation for its applications in tunable photonic microwave generation, AM-to-FM conversion, and dual-frequency precision Doppler lidar.     

基于偏振旋转光反馈下的外光注入VCSEL产生高性能毫米波

本文提出一种基于偏振旋转光反馈下的外光注入垂直腔 表面发射激光器(VCSEL)产生高性能毫米波的方案, 并利用描述外部扰动下VCSEL动态特性的自旋反转模型(SFM), 对所产生的毫米波的特性进行了数值研究. 研究结果表明: 一个受到主VCSEL(M-VCSEL)光注入的副VCSEL(S-VCSEL)在一定条件下可以产生单周期(P1)振荡, 即在光波上调制了一个微波信号. 通过调节外光注入强度ξ_i以及S-VCSEL与M-VCSEL之间频率失谐Δν, 可以获得频率在30---60 GHz范围内连续可调的毫米波信号. 在外光注入VCSEL中引入偏振旋转光反馈, 通过选取合适的反馈强度ξ_f以及反馈延迟时间τ, 产生的毫米波信号的线宽可以得到明显窄化. 对于光注入S-VCSEL所产生的线宽为5.509 MHz的毫米波, 在引入偏振旋转光反馈后, 毫米波线宽可以降低到230.2 kHz. 本文的研究对高速光载无线(RoF)系统中优质毫米波信号的获取具有一定的参考意义.     

混沌光注入垂直腔面发射激光器混沌输出的时延和带宽特性

提出并仿真论证了利用一个双光反馈垂直腔面发射激光器(定义为主VCSEL,M-VCSEL)产生的混沌光平行单向注入到另一个VCSEL(定义为副VCSEL,S-VCSEL)使所产生的混沌信号的延时特征(TDS)和带宽特性得以优化的技术方案.首先,基于VCSELs自旋反转模型,结合自相关分析方法,通过对系统参量进行优化,可使双光反馈M-VCSEL的X偏振分量(X-PC)和Y偏振分量(Y-PC)均输出混沌信号,且两路混沌信号的平均强度相当、TDS均较弱;在此基础上,将双光反馈M-VCSEL在优化条件下得到的混沌信号平行单向注入到S-VCSEL中,以获得两路TDS得到抑制、带宽更宽的混沌信号.通过考察两个偏振分量输出混沌信号的TDS以及混沌带宽在注入强度和频率失谐构成的参数空间的演化规律,确定了系统获取两路TDS被抑制、宽带宽的混沌信号所需的注入参数范围.     

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.     

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。     

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     

外腔光反馈的半导体激光器基本模型的运行模式

根据Lang-kobayashi带光反馈的半导体激光器模型,从理论上推导出其稳定条件.数学模拟表明,对于动态单模半导体激光器,少量的外光反馈也会改变激光器的输出模式,随着反馈量的增加,激光器的振荡模式亦增加,并始终为(2n+1)个模式.     

Experimental investigations on the external cavity time signature in chaotic output of an incoherent optical feedback external cavity semiconductor laser

Chaotic dynamics of a semiconductor laser subject to incoherent optical feedback (IOF) are experimentally investigated, and the external cavity time are retrieved and measured from intensity time series of the laser output by using self-correlation function and the mutual information. Through moderating feedback strength and injection current of the laser, the external cavity time signature of the laser chaotic output is effectively attenuated, and then the security of such chaos encryption system can be assured to a certain degree.     

Power fluctuations of a weakly optically-injected semiconductor laser in a period-one state

The frequency spectrum and the power output of a weakly optically-injected semiconductor laser in a period-one state are investigated. It is found that the oscillations in the power output consist of three components each caused by different physical effects, namely the relaxation oscillation frequency, the detuning between master and the slave laser frequency and the photon roundtrip time. For each set of parameters the spatio-temporal dynamics are obtained and the same internal oscillations occur.     

双光反馈半导体激光混沌系统的外腔反馈强度对延时特征的影响

通过构建一个双光反馈半导体激光混沌系统,本文实验研究了双腔之间不同反馈强度对系统混沌输出的延时特征的影响.结果表明:固定一个腔的反馈量,而适当调节另一个腔的反馈强度,可实现对混沌输出延时特征的良好抑制.同时,在延时反馈特征抑制较好的情况下,还存在时间漂移（即从混沌输出所提取的特征延时与系统真实延时之差）明显增大的现象.因此采用双光反馈半导体系统可以很好地隐藏激光混沌的延时参量,从而显著提升其在相关领域的表现性能.     

Generation and synchronization of feedback-induced chaos in semiconductor ring lasers by injection-locking

A smart scheme for chaotic signal generation in a semiconductor ring laser (SRL) with optical feedback is proposed and investigated numerically. The chaotic oscillation in the SRL can be generated by the partial reflection of the laser output. Time series, attracter and the power spectrum, as well as the Lyapunov exponent spectrum, are calculated and analyzed. We also study the synchronization scheme of feedback-induced chaos in SRLs by optical injection that consists of a drive SRL with optical feedback and a response SRL with optical injection from the drive laser. High-quality synchronization is achieved with suitable injection strength and detuning frequency between the drive and the response SRLs.     

Correlation dimension signature of wideband chaos synchronization of semiconductor lasers

Chaos data analysis has been performed on the chaotic output power time series data from a synchronized transmitter-receiver pair of semiconductor lasers. The system uses an asymmetric, bidirectional coupling configuration between the master (transmitter), which is a laser diode with optical feedback, and a stand-alone slave semiconductor laser. The correlation dimension of the chaotic time series has a minimum value of 4, which was obtained from high-bandwidth measurements. The correlation dimensions for both the master and the synchronized slave are identical when the cross-correlation coefficient of the synchronized chaos is above 0.9. These results establish correlation dimension analysis as an effective tool for the determination of the quality of wideband chaos synchronization.     

Influence of polarization mode competition on the synchronization of two unidirectionally coupled vertical-cavity surface-emitting lasers

We analyze theoretically the effect of polarization mode competition on the synchronization of two unidirectionally coupled vertical-cavity surface-emitting lasers (VCSELs). Chaos in the master laser is induced by delayed optical feedback, and the slave laser is subject to isotropic optical injection from the master VCSEL. We show that the synchronization quality can be enhanced when the chaotic regime in the master VCSEL involves both fundamental orthogonal linearly polarized modes.     

反馈强度对外腔反馈半导体激光器混沌熵源生成的随机数序列性能的影响

外腔反馈半导体激光器在合适的反馈强度下将呈现混沌态, 其输出的激光混沌信号可作为物理熵源获取物理随机数序列. 着重研究了外腔反馈强度对最后获取的二元码序列的随机性的影响. 数值仿真结果表明, 随着反馈强度的增加, 外腔反馈半导体激光器输出的混沌信号的延时时间特征峰值呈现先逐渐减小再逐渐增大的过程, 而对应的排列熵特征值呈现先增大、后缓慢降低的过程, 即存在一个优化的反馈强度可使输出的混沌信号的延时特征得到有效抑制且复杂度高. 利用NIST Special Publication 800-22软件对基于不同反馈强度下外腔半导体激光器输出的混沌信号所产生的二元码序列的随机性进行了相关测试, 并讨论了反馈强度的大小对测试结果的影响.     

Narrow bandwidth operation of high-power broad-area diode laser using cascaded phase-conjugate injection locking

A broad-area laser is injection-locked by another broad-area laser that is also injection-locked by a single-mode diode laser. Two double-phase conjugate mirrors of photorefractive BaTaO₃ are used to couple the master laser beams to the first slave laser, and the first slave laser output to the second slave laser. One of the double-phase conjugate mirrors is built up with the beams from two broad-area lasers. Two slave lasers are oscillating in single longitudinal mode at 808.5 nm and the spectral width is the same as that of the master laser. Final single-mode output power from the second slave broad-area laser is 840 mW, which is limited by the power of the injection beam. This work verifies the possibility of the multi-stage cascaded injection locking of high-power diode lasers with phase-conjugate injection. Received: 18 November 1998 / Revised version: 29 January 1999 / Published online: 7 April 1999