注入锁定TEA CO2激光器激光脉冲特性分析

本文在一般的TEACO₂激光器的动力学方程的基础上,给出注入锁定情况下TEACO₂激光器的动力学方程组,并进行数值计算,结果表明,TEACO₂激光器注入锁定激光脉冲宽度比自由运转时的变宽了,脉冲峰值功率降低,而且激光脉冲产生的时间提前,这与实验规律相吻合。     

脉冲CO2激光器的多频动力学模型

建立了适用于各种气压下(20×133-20×105 Pa)的脉冲CO2激光器的六温度多频动力学模型,该模型考虑了增益谱线重叠效应,序列带、热带的影响,以及非洛伦兹线型效应.对模型进行数值求解可以预言和解释不同气压下的脉冲CO2激光器的输出特性,有助于评价不同的抽运设计和研究可调谐特性,为设计脉冲CO2激光系统提供理论支持.     

小型多功能CO2激光器

研制了一种小型多功能CO2激光器。该激光器可以单脉冲、重频或连续方式输出,并可实现输出脉冲频率的编码及波长调谐。激光器谐振腔采用光栅一级振荡,零级输出的工作方式,分别利用声光调Q技术和脉冲放电技术实现了百ns至亚ms量级的脉冲激光输出。详细介绍了该激光器中基于光学角反射器原理设计的光栅调谐定向输出装置,并对其进行了理论计算和论证,实现了不同波长激光的定向、定位输出,获得调谐激光输出谱线超过60条,谱线分辨率优于0.01μm。激光器脉冲重复频率1Hz～10KHz连续可调,输出波长调谐范围9.2μm～10.8μm,激光器连续输出最大功率8W,重复频率1KHz时最小激光脉宽180ns,峰值功率4062W。该激光器在激光与物质相互作用科学领域,特别是激光对物质作用与破坏机理的研究方面具有重要的应用价值。     

谱线和耦合系数对光纤激光器相互注入锁定的影响

相互注入锁定是相干合成技术中最具发展前景的方案之一. 在两个光纤激光器相互注入锁定的基础上,利用可调节光纤光栅改变其中一个激光器的中心谱线和利用不同的分束器改变两个激光器间的耦合系数,同时监测两个激光器的远场光斑和谱线,判断激光器谱线和耦合系数对相互注入锁定的影响. 通过理论和实验得到：提高耦合系数可以提高锁定的频率差;两个激光器的谱线越接近锁定的效果越好,当激光器的谱线超过一定范围时,两个激光器将不能被锁定. 关键词： 光纤激光器 相干合成 相位锁定     

声光偏频亚多普勒光谱无调制激光频率锁定

将激光器锁定到合适的参考频率标准上 ,可以有效地改善激光器的频率稳定性。采用两个声光调制器(AOM) ,使铯原子D2 线饱和吸收光谱分别发生Ω±Δ绝对频移 ;通过改变射频压控振荡器 (RFVCO)的Vf 端口直流电压调节相对频移间隔Δ ,当相对频率间隔选择合适时两信号相减得到了类色散型鉴频曲线。实验中实现了85 2nm光栅外腔半导体激光器相对于铯原子D2 线6S1/2 F =4 6P3 /2 F′ =5超精细跃迁线 (中心频率ν0 )的无调制偏频锁定 (锁定后中心频率ν0 +Ω ,偏频量为Ω)。由闭环锁定后的误差信号估计 ,5 0s内典型的频率起伏小于± 2 70kHz ,较相同时间段内激光器自由运转时的频率起伏 14MHz有显著的改善。该方法可避免对激光器直接进行频率调制的常规饱和吸收锁频方案所引入的额外频率噪声和强度噪声。     

互注入锁定产生双波长可调谐光脉冲的实验研究

报道了两个增益开关调制的法布里-珀罗半导体激光器互注入锁定实验方案,可产生双波长可调谐光脉冲。该装置对两个结构基本相同的法布里珀罗半导体激光器做增益开关调制,产生多模光脉冲输出;然后利用两个光纤光栅作为滤波元件,通过调节可调谐光延迟线(VODL2),可使得双波长光脉冲在两个法布里-珀罗激光器之间相互注入锁定．从而在输出端得到高边模抑制比的双波长光脉冲输出。然后再通过应力作用在两个光纤光栅上以改变它们的反射波长和适当调整另一个可调谐光延迟线(VODLI)长度．可得到不同的双波长的光脉冲输出,而重复频率保持524．6MHz不变。在13．2nm调谐范围内边模抑制比高于25dB．系统稳定且波长调节方便。     

利用光频梳提高台阶高度测量准确度的方法

提出一种利用光频梳和可调谐半导体激光器提高台阶高度测量准确度的方法. 通过将可调谐激光器锁定至光频梳,可对激光器的输出波长进行精确锁定与测量.基于可调合成波长链原理,利用锁定后的半导体激光器构建了一套台阶高度测量方案,该方案可消除合成波长误差对台阶高度测量不确定度的影响. 采用一台可调谐半导体激光器和光频梳进行了5000 s的连续锁定实验, 结果表明,锁定后的可调谐半导体激光器的频率稳定度达 1.8×10^-12.该方法的理论测量不确定度约为7.9 nm, 且测量结果可溯源至时间频率基准.     

小型可调谐单纵模TEA CO2激光器

对在三镜腔中插入法布里-珀罗(F-P)标准具实现单纵模激光输出的方法进行了分析,计算了激光器的输出特性。设计研制了一台单纵模可调谐TEA CO2激光器。采用在三镜腔中插入F-P标准具的方法实现了单纵模激光的调谐输出。当激光器以5 Hz重复频率运转时,得到9P(16)谱线能量大于200 mJ,脉冲宽度约为150 ns。     

用可调谐CO_2激光器注入同步实现TEA—CO_2激光器的单纵模运转

用一台作为主控振荡器的可调谐CO_2波导激光器注入同步的方式实现TEA—CO_2激光器的频率调谐,采用的是特殊注入方法。在不同运转条件下,改变激光谱线、主控振荡器功率、偏离谱线中心频率等参量进行了同步实验。     

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     

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.     

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.     

Low-Frequency Fluctuation and Frequency-Locking in Semiconductor Lasers with Long External Cavity Feedback

The properties of low-frequency fluctuations in semiconductor lasers with optical feedback from a long external cavity are experimentally studied. Frequency-locking of the laser light output to the injection current modulation is observed when the modulation frequency approaches the external cavity mode. The modulation frequency for the successful frequency-locking is always less than the external cavity mode frequency and the locking domains as a function of the modulation amplitude is asymmetric with respect to the 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.     

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.     

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.     

Enhanced locking region in injection-locked two-section lasers

In this Letter, we investigate the criteria for achieving an enhanced stable locking region in the parameter space of injected field E_inj and frequency detuning ω in two-section semiconductor lasers subject to optical injection. Using the rate equations, a stability analysis is performed and the conditions for an enhanced locking region are deduced from the requirement for the average linewidth enhancement factor appearing in the locking-bandwidth equation to be close to zero. We calculate a stability map for an injection-locked two-section laser with an almost-symmetrical locking region that is greatly enhanced compared to a single-section injection-locked laser with identical material and control parameters.     

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     

Effect of frequency detuning on the output characteristics of CO<Subscript>2</Subscript> lasers

The effect of frequency detuning away from the line center on the radiative parameters of pulsed CO₂ lasers is studied by numerical modelling. It is shown that the temporal, energy, and spectral characteristics of the output can be controlled by varying the detuning and other parameters. Output pulses with a high peak power have an essentially unremovable, relatively long "tail" owing to the rotational bottleneck effect. The energy of the laser pulse is greatest at the line center. For certain values of the parameters, a maximum peak power is attained in the wings of the line, rather than at its center. The amount of sweeping depends on the sign of the detuning and is typically no more than 10 MHz.     

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.