高功率微波振荡器的相位控制

基于相对论返波管振荡器,提出了一种小信号牵引相位控制的方法,通过外加小信号对振荡器起振过程的引导,实现对输出微波的相位控制。相比于传统的方法,该方法可以利用ns量级的脉冲在较宽的带宽和较低的注入功率下实现对高功率微波振荡器的相位控制。在X波段相对论返波管振荡器相位控制实验中,利用百kW级的小信号,实现了对GW级高功率微波的输出相位控制,相位抖动小于±15°。     

Influence of timing jitter on nonlinear dynamics of a photonic crystal fiber ring cavity

We demonstrate that timing jitter has a strong influence on supercontinua generated in a photonic crystal fiber ring cavity synchronously pumped by 140?fs pulses. The global dynamics with respect to cavity detuning is analyzed both numerically and experimentally by tracking the cavity pulse energy. The results show that low-frequency timing jitter, induced by both the pump oscillator and the external cavity, masks the fine underlying bifurcation structure of the system. Numerical simulations in the absence of timing jitter reveal that the system dynamics fall into four qualitatively different regimes. The existence of these regimes is experimentally observed in first-return diagrams.     

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.     

Experimental investigation of the impact of optical injection on vital parameters of a gain-switched pulse source

An analysis of optical injection on a gain-switched distributed feedback (DFB) laser and its impact on pulse parameters that influence the performance of the pulse source in high-speed optical communication systems is presented in this paper. A range of 10 GHz in detuning and 5 dB in injected power has been experimentally identified to attain pulses, from an optically injected gain-switched DFB laser, with durations below 10 ps and pedestal suppression higher than 35 dB. These pulse features are associated with a side mode suppression ratio of about 30 dB and a timing jitter of less than 1 ps. This demonstrates the feasibility of using optical injection in conjunction with appropriate pulse compression schemes for developing an optimized and cost-efficient pulse source, based on a gain-switched DFB laser, for high-speed photonic systems.     

加速器噪声对远红外FEL振荡器影响的模拟研究

 采用FEL一维脉冲模型，针对中国原子能研究院的远红外FEL振荡器，模拟研究了加速器噪声对FEL的影响。对电子束微脉冲的时间晃动和能量波动所引起的光功率波动及光谱中心晃动进行了模拟计算，在计算中还分别考虑了噪声频率、振幅的大小产生的直接影响以及腔失谐的间接影响。     

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。     

储存环束流Robinson不稳定性的分析和测量

 探讨了储存环束流的Robinson不稳定性问题,提出用“等效失谐角大于零”取代“失谐角大于零”作为束流稳定的基本条件。在合肥光源电子储存环200 MeV注入状态下,对束流不稳定性与高频腔失谐之间的关系进行了实验测量。结果表明：当束流稳定条件不满足时,如果高频腔大失谐,束流将全部丢失;小失谐时束流容易部分丢失;当高频腔处于负失谐状态,束流流强将限制在较低水平。     

Polarization Switching Bistability and Dynamics in Vertical-Cavity Surface-Emitting Laser under Orthogonal Optical Injection

Bistability as well as dynamics associated to polarization switching in a vertical-cavity surface-emitting laser (VCSEL) submitted to orthogonal optical injection from an external master laser are investigated. Intensity-polarization switching bistability is studied by increasing and decreasing the intensity of the injected beam and for a fixed frequency detuning, i.e. the frequency offset between master and the free running VCSEL. Depending on the frequency detuning, bistable switching is experimentally found to occur with or without injection locking of the fundamental mode to the master laser frequency. For large positive detuning, injection locking of the first-order transverse mode with a strong depression of the fundamental mode has been observed. The case of frequency – polarization switching bistability, i.e. when the frequency detuning is first decreased and then increased for a fixed injected power, has also been theoretically analyzed. Qualitative comparison with previous experimental work is presented for the dependence of the width of the bistable switching region on the injection strength level. Finally we show an experimental result of complicated dynamics including period doubling route to chaos that accompany polarization switching and which motivates future theoretical investigations.     

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     

Ultrafast mode switching based on a micro-ring laser

Injection locking and multi-mode switching characteristics of a semiconductor ring laser with the radius of 10 μm are investigated based on a nonlinear time domain multimode rate-equation model. The stable injection locking regions for different target modes are studied as the function of detuning frequency and injection power ratio. The results show that ultra-wide detuning range of ∼100 GHz wide at 5 dB injection power ratio and ultra-low switching power ratio of −27 dB can be realized for this micro-ring laser device. Optimal detuning value and high injection power lead to the minimal switching time. An ultrafast response time of 10 ps indicates that a 10 μm-radius SRL can be utilized for ultrafast all-optical scenarios and high-speed tunable lasers.     

自触发紫外预电离开关脉冲击穿时延抖动影响因素及改进方法

研究了一种自触发紫外预电离开关击穿时延抖动特性的影响因素,结果表明:触发间隙电容放电阶段起预电离作用时,预电离注入时刻开关电场是开关时延抖动的决定性因素,提高工作系数和采用逸出功更低的电极材料对降低开关在脉冲峰值附近击穿时的时延抖动效果有限。提出的改进方法为:减小开关均压电阻阻值,显著延长触发间隙的有效燃弧时间,消除预电离注入时间及抖动的影响。采用改进方法时可以使开关在工作电压300～800 kV、前沿100 ns、180 ns的脉冲峰值附近击穿时的时延抖动分别小于1.3 ns、2.8 ns。     

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.     

High Quality Factor Q and Low Timing Jitter from MLLD Using Optical Injection

采用１０ＧＨｚ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用混合锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００．     

用光脉冲注入从锁模激光二极管再生低抖动高Q值光时钟

采用１０ＧＨＺ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用给锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００。     

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     

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.     

Locking bandwidth and birefringence effects for polarized optical injection in vertical-cavity surface-emitting lasers

The aim of this paper is to investigate the effects of external optical injection taking account of polarization and electron spin properties in vertical-cavity surface-emitting lasers (VCSELs). Using external polarized injection we seek the locked phases and amplitudes of specific polarized fields in terms of injection level and frequency detuning, taking account of two kinds of distinguishable carrier density (spin-up and spin-down). For the conventional form of optical injection without taking account of spin-polarized fields there are three fundamental equations describing the carrier density, field amplitude and phase. However, by using the spin flip model (SFM), the combined effect of polarized fields along two perpendicular crystal axes and electron spin properties results in six equations. We analyse the conditions for stable locking and also the influence of birefringence effects on the stability map of detuning versus optical injection for both cases of injection polarized parallel and perpendicular to the lasing mode of the solitary VCSEL. For given values of pumping and spin relaxation rate there is a minimum birefringence rate for orthogonal injection. Above this value three regions of elliptical polarization are found in the stability map, namely “quasi-stability” (QS), “coupled limit cycle” (CLC) and “coupled chaos” (CC). The three regions of linear polarization, namely chaos, limit cycle and stability, are reduced in area compared to the case of parallel injection. For orthogonal injection it is found that increased birefringence or reduced spin relaxation rate causes the stable locking region to begin at higher injected power and frequency detuning.     

Polarization switching and synchronization of mutually coupled vertical-cavity surface-emitting semiconductor lasers

Polarization switching (PS) dynamics and synchronization performances of two mutually coupled vertical-cavity surface-emitting lasers (VCSELs) are studied theoretically in this paper. A group of dimensionless rate equations is derived to describe our model. While analysing the PS characteristics, we focus on the effects of coupling rate and frequency detuning regarding different mutual injection types. The results indicate that the x-mode injection defers the occurrence of PS, while the y-mode injection leads the PS to occur at a lower current. Strong enough polarization-selective injection can suppress the PS. Moreover, if frequency detuning is considered, the effects of polarization-selective mutual injection will be weakened. To evaluate the synchronization performance, the correlation coefficients and output dynamics of VCSELs with both pure mode and mixed mode polarizations are given. It is found that performance of complete synchronization is sensitive to the frequency mismatch but it is little affected by mixed mode polarizations, which is opposite to the case of injection-locking synchronization.     

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.     

外部光注入空间耦合半导体激光器高维混沌系统的增频与控制研究

提出外部光注入空间耦合半导体激光器系统,研究 外部光注入两激光器混沌振荡频率增强以及混沌控制等特点, 给出稳定频率失谐公式.研究表明,当单激光器注入时,注入激光器 呈现出三个混沌扩频区域;发现在强激光注入条件下,随着注入程度的 增加,注入激光器混沌振荡频率增强非常有效且可达到 3.5倍以上(尽管另一个激光器频率会缓慢下降); 随着注入光正频率失谐的增加,两激光器混沌振荡都能进一步增 强;发现混沌控制窗口,即在弱注入条件下两激光器可以被控制到单周 期、双周期、四周期、六周期等.当双激光器注入时,随着注入程度 的增加,两激光器混沌振荡频率 进一步增加, 且可达到3.5倍和2.65倍以上; 随着注入光正频率失谐增加, 两激光器混沌振荡频率增加.双激光器注 入控制混沌的一个窗口也被发现:即在强注入条件下两激光器可以被 控制到单周期、三周期、六周期等.最后详细给出了单激光注入系 统从单周期模式锁定到类周期再进入混沌增频的发展路径以及双 激光注入系统从混沌到类周期再进入单周期模式锁定的演化控制路径等.