基于光电负反馈的光注入1550nm垂直腔面发射激光器产生窄线宽微波信号

基于1 550nm垂直腔面发射激光器在平行偏振光注入下呈现的单周期非线性动力学状态,进一步引入光电负反馈,得到了高质量的微波信号.实验研究结果表明:平行偏振光注入下,通过调节注入光的注入强度及频率,1 550nm垂直腔面发射激光器可呈现注入锁定、单周期、倍周期、混沌等多种非线性动力学状态;在合适的注入参量下,平行偏振光注入1 550nm垂直腔面发射激光器可产生光谱具有单边带结构、频率超过10GHz的光子微波信号,但该微波信号的线宽较宽(达MHz量级);进一步引入光电负反馈后,通过选取合适的光电反馈强度,可将该微波信号的线宽减小至一百多kHz(减小两个量级以上);在选择优化的反馈强度条件下,仅通过简单调节注入光强度,可实现窄线宽光子微波信号的频率在一定范围内连续可调谐.     

Theory of stability and bifurcation in a multi-quantum well laser with opto-electronic delayed feedback

This paper presents an opto-electronic feedback multi-quantum well laser system and outlines our study of the dynamics and bifurcation in a multi-quantum well laser due to the opto-electronic delayed feedback effect. We point out theoretically the conditions of stability and Hopf bifurcation of the laser. The relaxation oscillation frequency of the system is educed to be the function of the feedback level, delayed time and in-current. The route from stability to bifurcation is numerically simulated via varying the delayed time, feedback strength and in-current. The results show that the induced dynamics can be grouped into four distinct types or modes (stable, periodic pulsed, undamped oscillating or beating, and chaos), where the frequency and intensity varying with the delayed time in the two periodic regions are analyzed detailedly to find that the pulsing frequency is reduced with the long delayed time while the pulsing intensity is added with the long delayed time. And the chaotic pulsing frequency is increased with the large in-current. In addition, the carrier transport between the barrier region and the active region can characterize the dynamics in the laser to produce stable, periodic pulsed, beating and chaotic states by altering the carriers transport or escape rate value.     

Numerical investigation on photonic microwave generation by a sole excited-state emitting quantum dot laser with optical injection and optical feedback

Based on three-level exciton model, the enhanced photonic microwave signal generation by using a sole excited-state(ES) emitting quantum dot(QD) laser under both optical injection and optical feedback is numerically studied. Within the range of period-one(P1) dynamics caused by the optical injection, the variations of microwave frequency and microwave intensity with the parameters of frequency detuning and injection strength are demonstrated. It is found that the microwave frequency can be continuously tuned by adjusting the injection parameters, and the microwave intensity can be enhanced by changing the injection strength. Moreover, considering that the generated microwave has a wide linewidth, an optical feedback loop is further employed to compress the linewidth, and the effect of feedback parameters on the linewidth is investigated. It is found that with the increase of feedback strength or delay time, the linewidth is evidently decreased due to the locking effect. However, for the relatively large feedback strength or delay time, the linewidth compression effect becomes worse due to the gradually destroyed P1 dynamics. Besides, through optimizing the feedback parameters, the linewidth can be reduced by up to more than one order of magnitude for different microwave frequencies.     

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.     

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     

Periodic and chaotic oscillations in mutual-coupled mid-infrared quantum cascade lasers

Dynamic states in mutual-coupled mid-infrared quantum cascade lasers (QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang—Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ_inj, 2τ_inj, and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution. This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.     

The use of nonlinear dynamics of erbium-doped fiber laser at pump modulation for intra-cavity sensing

We report the use of nonlinear dynamics of an erbium-doped fiber laser (EDFL) at pump modulation, namely the period-1 pulsed regime, for intra-cavity loss sensing and demonstrate noticeable sensitivity enhancement of an EDFL-based sensor, provided by this arrangement. Experimentally, we obtain a ten-fold increase of the sensor response, i.e. peak-to-peak pulse amplitude against loss variation, as compared with the standard sensing schemes using a low-power wide-spectrum light emitting diode (LED) or fiber laser without external modulation. This advantage originates from a strong dependence of pulse amplitude in the period-1 regime on intra-cavity loss variable that is, in turn, determined by the interrelation of relaxation frequency (an internal EDFL parameter) and frequency and depth of external (pump) modulation. A modeling of the EDFL-based sensor, presented for the case when the laser operates in the period-1 regime, allows an insight into the sensor operation details and opens the gate to its further optimization. The proposed sensing method seems to be a proper choice for the applications where an intra-cavity sensor’s head has high internal loss (≥10 dB) while sensed loss is varied within a quite narrow range (a few dB).     

Control of period-one oscillation for all-optical clock division and clock recovery by optical pulse injection driven semiconductor laser

The period-one oscillation produced by an external optical pulse injection driven semiconductor laser is applied to clock recovery and frequency division. By adjusting the repetition rate or injection power of the external injection optical pulses to lock the different harmonic frequencies of the period-one state, the clock recovery and the frequency division （the second and third frequency divisions） are achieved experimentally. In addition, in frequency locking ranges of 2 GHz and 1.9 GHz, the second and third frequency divisions are obtained with the phase noise lower than 100 dBc/Hz, respectively. Our experimental results are consistent well with the numerical simulations.     

Stable single-mode operation of injection-seeded Q-switched Nd:YAG laser by sine voltage modulation

Based on the modified ramp and fire technique, a novel injection seeding approach with real-time resonance tracking is successfully demonstrated in a single-frequency Nd:YAG pulsed laser. Appling a high-frequency sinusoidal modulation voltage to one piezo actuator and an adjustable DC voltage to another piezo actuator for active feedback, single-mode laser output with high-frequency stability is obtained, and the effect of the piezo hysteresis on the frequency stability can be eliminated for a laser diode pumped Q-switched Nd:YAG laser at a repetition rate of 400 Hz.     

线宽增强因子对外光注入半导体激光器非线性单周期振荡特性的影响

线宽增强因子是影响半导体激光器输出特性的一个重要参量,不同材料不同结构类型的半导体激光器的线宽增强因子有较大的差异.利用光注入半导体激光器的单模速率方程模型,数值研究了线宽增强因子对外光注入半导体激光器的非线性单周期振荡特性的影响.结果表明:外光注入半导体激光器的动态特性对线宽增强因子的变化极为敏感,随着线宽增强因子的增加,在负失谐注入范围内单周期振荡区域显著增大,同时注入锁定的稳态输出被大大抑制.分析了线宽增强因子对非线性单周期振荡光谱特性和振荡频率的影响,结果表明:随着半导体激光器线宽增强因子的增大,单周期振荡的频率越大|当线宽增强因子不变时,单周期振荡的频率随注入光强度和频率失谐的增加而增加.     

激光回馈效应及其传感应用研究的进展

对基于激光回馈效应的传感应用研究进展进行了综述。由于激光回馈引起激光器功率波动一个条纹对应外部反射镜移动半个光波波长,功率波动深度与传统双光束干涉系统相当,基于该现象的激光回馈干涉仪与传统的干涉仪相比具有相同的相位灵敏度。但其结构简单、紧凑、易准直的特点,引起了国内外科研者浓厚的兴趣,开发了很多全新概念、经济实用的精密测量仪器。对激光回馈效应在位移测量、速度测量、振动测量、距离测量、角度测量和形貌测量中的原理进行了介绍,同时对各传感应用系统进行了评述。     

激光诱导击穿光谱脉冲激光功率锁定的研究

激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)在煤质在线监测方面展现了突出的应用前景和研究价值。针对该技术在实际应用中会由于脉冲激光功率起伏导致的长期测量稳定性差的问题,建立了闭环负反馈式脉冲激光功率锁定装置,采用激光功率负反馈信号控制和锁定Nd∶YAG激光器输出功率。实验研究了不同分光比例脉冲激光器锁定在设定输出功率,同一分光比例激光器锁定在不同输出功率以及长时间运行时的功率锁定。结果表明,不同的分光比例对激光输出功率的锁定效果影响不大,分光比例越小,稳定速度越快;同一分光比例实现激光脉冲功率不同预设值的锁定以及在长时间运行时,采用此装置进行功率锁定后,激光输出功率处于预设区间内,RSD值由自由运行时的2.4%降低至1.1%。     

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.     

Proposal for a chaotic ratchet using cold atoms in optical lattices

We investigate a new type of quantum ratchet which may be realized by cold atoms in a double-well optical lattice, pulsed with unequal periods. The classical dynamics is chaotic and we find the classical diffusion rate D is asymmetric in momentum up to a finite time t(r). The quantum behavior produces a corresponding asymmetry in the momentum distribution which is "frozen-in" by dynamical localization provided the break time t(*)>or=t(r). We conclude that the cold atom ratchets require Db/ variant Planck's over 2pi approximately 1, where b is a small deviation from period-one pulses.     

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.     

Slave-master dynamics of semiconductor laser with short external cavity

In this paper, the dynamical response of a slave semiconductor laser, with short cavity, under injection of a chaotic light from a master semiconductor laser has been widely studied. This is analyzed numerically via bifurcation diagrams, in terms of the phase and strength of the feedback, as control parameters. It is shown that, both of these parameters should be considered in the dynamical response of the slave laser. Our numerical calculations show that the dynamics of the slave laser imitates the master laser, in addition to the feedback strength, it also heavily depends on the injection dynamics and rates. Numerical results also show that for different values of the control parameters, the intensity of the slave laser output can be fully different from the injection source. However, we found out under appropriate conditions, that the dynamics of the slave can be the same as the master laser. The results also show that the output of the slave laser, compared to its output without injection, can be stabled in the appropriate values of the injection rate from the master laser.     

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.     

Effect of linewidth enhancement factor on the stability map of optically injected distributed feedback laser

We theoretically investigate the effect of the linewidth enhancement factor (known as the α-factor) on the nonlinear dynamics of a distributed feedback (DFB) laser subjected to external coherent optical injection. This factor has shown considerable effect on the behavior of the injected laser, as shown in the so-called stability map.     

LED pumped polymer laser sensor for explosives

A very compact explosive vapor sensor is demonstrated based on a distributed feedback polymer laser pumped by a commercial InGaN light‐emitting diode. The laser shows a two‐stage turn on of the laser emission, for pulsed drive currents above 15.7 A. The ‘double‐threshold’ phenomenon is attributed to the slow rise of the ∼30 ns duration LED pump pulses. The laser emits a 533 nm pulsed output beam of ∼10 ns duration perpendicular to the polymer film. When exposed to nitroaromatic model explosive vapors at ∼8 ppb concentration, the laser shows a 46% change in the surface‐emitted output under optimized LED excitation.     

具有自动跟踪功能的新型光纤光栅振动传感器

振动传感技术是分析机械动力学的重要手段之一,结合光纤Bragg光栅（FBG-Fiber Bragg Grating）传感系统的特点,提出了一种新型的光纤Bragg光栅振动传感器的设计,该传感器的新颖之处在于提出了一种用反馈电路实现的对光纤Bragg光栅反射波长移位进行自动践踏的探测方法。该反馈电路用以驱动法布里-珀罗腔（F-P-Fabri-Perot）。利用当法布里-珀罗腔满足特定条件时其透射光可达到最强或最弱原理,建立了F-P腔解调系统模型。