半导体光纤环形激光器输出状态分析与分类

研究了不同注入电流、不同输出偏振度下,半导体光纤环形激光器输出光的混沌特性.分别采用时域观察法、C-C法、Wigner-ville分布时频分析法、最大Lyapunov指数法联合分析输出光的时域、频域统计特性.从而将激光器输出按偏振度划分为三类:偏振度在0%到20%,随着电流的增大,激光器输出偏振混沌激光,其类型发生阶跃性跳变;偏振度在30～80%,激光器输出仍以偏振混沌激光为主,其类型不随电流增大而发生跳变;偏振度趋于90～100%,激光器输出以强度混沌激光为主,偏振混沌光随着偏振度趋向100%而下降为零.利用虚假邻点法计算嵌入维数和回归图法重构吸引子,得到上述三种输出类型的复杂程度依次是:椭圆吸引子(6维)、方形吸引子(7维)、点形吸引子(5维).由此得出,半导体光纤环形激光器用于偏振混沌通信的最佳区域为:偏振度处于30%至80%,注入电流处于330 mA～550 mA.     

2.1 μm可调谐多波长掺钬光纤激光器

为了实现2.1 μm波段光纤激光器输出多波长激光，设计了一种基于光纤Sagnac干涉仪的可调谐多波长掺钬光纤激光器。采用1.9 μm波段掺铥光纤激光器泵浦一段长3 m的掺钬石英光纤，获得2.1 μm波段的光放大；环形腔中，由保偏光纤和偏振控制器构成的光纤Sagnac干涉仪，实现2.1 μm波段周期滤波，获得了2.1 μm波段多波长激光，输出功率1 mW~15 mW可调谐，最多可观测到6个波长的激光输出。通过调节环形腔内偏振控制器，能够实现2.1 μm波段1~6个波长的调谐。     

混沌光纤围栏系统及其入侵定位方法

提出一种基于半导体光纤环形激光器的混沌光纤围栏系统。在该系统中,激光器输出为具有帧结构的偏振混沌光,环形激光器中的一段光纤用作传感光纤。任意位置的入侵都会改变光纤的双折射分布状态,引起环形激光器初始状态的改变,由于混沌对初值的敏感性,激光器输出波形即刻被改变。通过相邻帧输出波形的互相关检测可实现入侵的检测。利用混沌环形激光器输出波形的帧型特点实现入侵定位的空间-时间转换。利用入侵位置与帧间互相关峰值的对应关系实现入侵的定位。该方法实时性好,抗干扰性强,检测结果不受周围环境变化影响。实验结果表明,在3 km左右的监测范围内定位误差约45 m,相对误差5%,且检测结果重复性良好。     

光注入掺铒光纤激光器的混沌特性

对光注入情况下混沌光纤激光器的输出特性进行实验研究.混沌光纤激光器采用环形腔结构,利用光纤的非线性克尔效应产生混沌激光.主激光器产生的混沌激光通过光隔离器和光纤耦合器注入到混沌掺铒光纤激光器实现外光注入.将主激光器产生的不同功率的混沌信号注入从激光器,研究光注入后从激光器混沌信号时序、频谱、自相关以及稳定性与复杂度等特性.结果 表明,光注入后的混沌信号时序随机且幅度频数呈高斯分布,频谱无明显的周期特性,自相关特性优良.光注入掺铒光纤激光器混沌输出在保证混沌源高复杂度的同时提高了混沌源的稳定性.     

基于匹配干涉仪的光纤环形激光相干坍塌抑制

跳模会导致单波长光纤环形激光器相干性有不同程度的退化,严重影响光学系统的性能。设计一种基于匹配干涉仪的相干坍塌抑制方案,分析抑制机理。并分别搭建臂差可调的空间光匹配干涉仪(SLMI)和全光纤结构匹配干涉仪(AFMI),通过实验对抑制效果进行方案验证。结果表明:当SLMI的等效臂差不断逼近理论值时,可监测到多模匹配干涉现象,该现象等效于单纵模激光干涉,从而实现相干坍塌抑制;AFMI结构紧凑,便于嵌入光纤相干探测系统中,能有效抑制随机跳模引入的相干坍塌和相位噪声谱级的大幅上升,降低系统虚警概率。作为一种被动手段,匹配干涉仪对抑制或规避模式失稳引起的相干坍塌具有指导意义。     

环形光纤孤子激光器

本文对2.5Gb/s环形光纤孤子激光器进行了实验研究。采用半导体光放大器作为光调制器,其实测的脉冲宽度小于30ps,谱宽为0.12nm;经过50km色散位移光纤后,其孤子脉冲宽度与谱宽基本保持不变。     

Sagnac干涉仪与光纤环形激光器

依据相干光学理论,以现代激光干涉侧试技术中的光纤Ｓａｇｎａｃ干涉仪为例,分析和讨论了光纤环形激光器的基本工作原理,并结合其物理原理简要介绍了光纤环形激光器和光纤陀螺（ＦＯＧ）的应用的发展前景。     

外腔延时反馈半导体激光器混沌偏振可调控制方法研究

提出外腔延时反馈半导体激光器混沌偏振可调控制方法,分别建立了垂直正交偏振延时双反馈、同偏振面方向延时双反馈以及任意可调偏振延时双反馈激光动力学物理模型. 通过调节激光器外腔光路中的平面镜和光衰减器可控制一平面偏振反馈光的延时时间及光反馈量,或调节一偏振反馈光的偏振面到另一个偏振反馈光的偏振面方向上或者到任意偏振方向都可进行激光混沌控制. 数值结果证明该方法可以控制激光混沌到单周期态、多周期态等,还发现该控制可使激光器同时呈现偏振周期振荡、偏振反周期振荡、稳定三种动力学行为等. 关键词： 混沌 控制 激光器 偏振     

一种新型自激发布里渊掺铒光纤激光器

利用级联的受激布里渊效应,自激发布里渊掺铒光纤激光器可以实现常温下的多波长激光输出。通过在自激发掺铒光纤激光器中引入一个高双折射萨尼亚克(Sagnac)环形滤波器,调节萨尼亚克环形滤波器的偏振控制器(PC),实现了可调谐多波长输出,同时在实验中观测到双布里渊多波长带的现象。研究了这种光纤激光器中萨尼亚克环形滤波器的带宽和980 nm抽运光功率对输出波长数的影响,在萨尼亚克环形滤波器的带宽为83.3 nm以及980 nm抽运光功率为260 mW时,得到了52个间隔为0.088 nm的多波长激光输出。     

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     

Pulse timing-jitter reduction by incoherent addition

A new technique is proposed and demonstrated for reducing the timing jitter of a mode-locked laser diode by use of fiber-optic interferometers with an optical path difference much longer than the laser's coherence length. At the output of the interferometer the intensities of the two pulse trains are incoherently added, giving rise to the cancellation of timing noise at specific Fourier frequencies determined by the path difference. The timing jitter of pulse trains emitted by a 19.444-GHz mode-locked laser is reduced to 0.991 and 0.874 ps for 100-kHz-18-MHz bandwidth after the pulse trains pass through a cascaded Mach-Zehnder and a ring interferometer, respectively.     

Synchronization of chaotic VCSELs by external chaotic signal parameter modulation

Synchronization of chaotic vertical-cavity surface-emitting lasers （VCSELs） is achieved by external chaotic signal modulation successfully. Simulation indicates that we can get chaos synchronization if the intensity of external chaotic signal is large enough. First of all, we use direct current modulation to achieve the chaos of VCSELs, and determine the laser＇s chaotic state by analyzing time series of the output and the corresponding power spectrum. And then we achieve synchronization of the two chaotic systems by external chaotic signal parameter modulation. We also find that the larger the modulation intensity is, the easier it is to achieve synchronization for chaotic VCSELs. This approach can also be applied to systems with a number of modulated lasers.     

多波长混沌掺铒光纤环形激光器实验研究

利用掺铒光纤环形激光器(EDFRL),基于光纤的非线性克尔效应,实验实现了多波长混沌激光输出。实验研究了EDFRL在时序上通过倍周期进入混沌的路径,并进行了理论分析,理论研究与实验结果一致。实验结果表明,随着抽运功率的增加,其光谱的输出呈现多波长,激光器最多可输出5个不同波长的混沌激光。采用光纤光栅进行滤波后,各个波长的输出均呈现混沌状态。     

Broad tunability of erbium-doped fiber ring laser based on few-mode polarization maintaining fiber Sagnac interferometer

A highly stable erbium-doped fiber (EDF) ring laser with broad tunability is proposed and experimentally demonstrated. It is accomplished by using a few-mode polarization maintaining fiber (FM-PMF) Sagnac interferometer, in which simultaneous Sagnac and modal interferences occur. Continuously tunable output is obtained by exerting the longitudinal strain on the FM-PMF in combination with adjusting a polarization controller (PC) next to the FM-PMF in the Sagnac interferometer. In addition, the adverse impact of uneven EDF gain distribution on the laser output power uniformity may be offset by the PC-dependent transmission loss of the FM-PMF Sagnac interferometer and reflected backward C-band amplifier spontaneous emission from the pumped EDF. During the whole tuning process, the tunable span covers more than 40 nm with the output power flatness better than 1 dB, 3 dB spectral linewidth narrower than 0.1 nm and optical signal-to-noise extinction ratio higher than 45 dB.     

Two‐dimensional microcavity lasers

Advances in processing technology, such as quantum‐well structures and dry‐etching techniques, have made it possible to create new types of two‐dimensional (2D) microcavity lasers which have 2D emission patterns of output laser light although conventional one‐dimensional (1D) edge‐emitting‐type lasers have 1D emission. Two‐dimensional microcavity lasers have given nice experimental stages for fundamental researches on wave chaos closely related to quantum chaos. New types of 2D microcavity lasers also can offer the important lasing characteristics of directionality and high‐power output light, and they may well find applications in optical communications, integrated optical circuits, and optical sensors. Fundamental physics of 2D microcavity lasers has been reviewed from the viewpoint of classical and quantum chaos, and recently developed theoretical approaches have been introduced. In addition, nonlinear dynamics due to the interaction among wave‐chaotic modes through the active lasing medium is explained. Applications of 2D microcavity lasers for directional emission with strong light confinement are introduced, as well as high‐precision rotation sensors designed by using wave‐chaotic properties.     

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.     

Chaotic dynamics of erbium-doped fiber laser with nonlinear optical loop mirror

We experimentally and numerically demonstrate the chaotic dynamics of the erbium-doped fiber laser with a nonlinear optical loop mirror. When the polarization controllers are fixed at an appropriate orientation, we observe that the fiber laser exhibits a period-doubling route to chaos with increasing the pump power in the experiment and simulation. The numerical simulation shows a good agreement with the experimental results. The results show experimentally and numerically that the chaotic dynamics of the erbium-doped fiber laser is related to the polarization state and the pump power of light in the cavity.     

Tunable 19 × 10 GHz L-band FP-SOA based multi-wavelength mode-locked fiber laser

We present a multi-wavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a Fabry-Perot semiconductor optical amplifier (FP-SOA). Because the gain of the SOA is depleted by an external injection optical signal, the SOA acts as a loss modulator. The FP-SOA serves as a tunable comb filter. The presented laser source can generate 19 synchronized wavelength channels with the extinction ratio of about 21 dB, each mode-locked at 10 GHz, and mode-locked pulse width is about 40 ps. Oscillation wavelengths band can be tuned by adjusting the bias current of the SOA, and wavelength spacing also can be changed by using a tunable optical delay line (ODL) or a temperature controller. The polarization-insensitive devices ensure that the output power is rather stable. This fiber laser has potential applications in longer waveband (L-band) within the low-attenuation window.     

低噪声环形腔掺铒光纤激光器的研究

分析了环形腔掺铒光纤激光器的输出特性,给出了稳态下的激光器输出功率、阈值泵浦功率和斜率效率的解析表达式,为激光器结构的优化提供了依据。搭建了全保偏环形腔掺铒光纤激光器,利用未泵浦铒纤中由驻波干涉和饱和吸收诱发的自写入光纤光栅的窄带滤波特性及反射波长的自适应特性,有效地解决了激光器的跳模问题。通过测量得到激光器系统的泵浦阈值为15.3mW,斜率效率为2.8%,输出偏振度为32dB。利用非平衡光纤干涉仪系统和相位产生载波(PGC)调制解调技术测得激光器的相位噪声为3×10-5rad/Hz~1/2(1kHz)。     

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.