用染料荧光增益增强弱增益拉曼模式的受激拉曼散射的经典理论

建立了用染料荧光增益增强弱拉曼模式的受激拉曼散射(SRS)的经典理论,详细给出了拉曼增益gR,染料荧光增益gD和总损耗α的表达式,并在其推导过程中对经典理论作了修正,最后得到了荧光增益和受激拉曼增益可以共同使SRS强度的指数部分快速增长的结果,可以很好地解释观察到的实验现象,并为其提供理论依据。     

用激光增益获取弱增益拉曼模式的受激拉曼散射光谱

当酒精的弱增益拉曼模式处于罗丹明640染料分子的激光增益范围时，在由悬垂液滴构成的圆形谐振腔中，观察到乙醇分子C—H伸缩系列模中多个弱增益拉曼模式的受激拉曼散射（SRS）光谱.随着抽运光的增强，迅速增长的强增益拉曼模式的受激辐射抑制了其他弱增益模式的SRS，并导致染料激光的完全淬灭.通过分析圆形腔腔模的光子速率方程和激光染料分子的三能级粒子数速率方程，解释了观察到的实验现象. 关键词： 受激拉曼散射 悬垂液滴 弱拉曼增益模式 激光增益     

变温条件下受激布里渊散射增益系数的实验测量

从理论及实验上分析了介质温度对受激布里渊散射(stimulated Brillouin scattering, SBS)阈值及增益系数的影响.在理论分析的基础上, 提出了一种通过测量SBS阈值来决定介质SBS增益系数的新方法. 实验及测量结果表明, SBS增益系数会随着介质温度的增加而呈现指数上升的趋势. 关键词： 受激布里渊散射 阈值 增益系数     

布里渊放大器中Stokes光的高增益放大

微小Stokes信号光在布里渊放大器中得到放大,当Stokes信号光强度为015mj时,增益系数达到67。Stokes光增益决定于Stokes信号光强度及放大池中泵光与Stokes光的耦合程度,小信号Stokes光将得到较大的增益,并能得到较好的相位共轭效果     

激光电子散射中的最大可能增益

借鉴自由电子激光(FEL)发展之初Madey对自由电子激光器中受激辐射引起的增益的讨论,通过在激光场中的量子电动力学(QED)的模型中引入激光电子系统初态态密度以及由不确定的系统初态到确定光子末态的跃迁速率,推导了激光电子正碰过程中受激辐射至单一电磁模式产生的最大可能增益。采用成功得到X射线或γ射线光子的三个激光电子Compton背散射实验的实验参数计算了激光电子散射过程中的最大可能增益,与第一台X射线自由电子激光(XFEL)中的最大可能增益作比较,进而对激光电子散射作为激光光源的可行性进行评估。计算结果表明,现有的能够得到X射线光子或γ射线光子的激光电子散射实验中的最大可能增益远低于第一台XFEL中的。本工作未能找到合适的激光电子参数以获得比第一台XFEL中更高的最大可能增益,但是在入射电磁波位于射频波段范围内找到了能够实现较高增益的参数组合。     

水体参量对受激布里渊散射阈值及增益的影响

针对水中受激布里渊散射阈值和增益这两个重要特征参量,理论分析了温度和盐度对水中受激布里渊散射增益的影响,同时采用耦合波方程与平均衰减系数相结合的方法,研究了阈值与温度和衰减系数的相关性。研究结果表明,受激布里渊散射的增益与温度和盐度正相关,随着温度和盐度的升高,受激布里渊散射增益增大;而受激布里渊散射阈值随着温度的增加而减小,随着衰减系数的增大而增大。研究结果对了解水中的受激布里渊散射过程提供理论依据。     

在同种光纤中实现RFA增益平坦化的方法

提出了一种新的光纤拉曼放大器设计方法:在同一种光纤内运用不同波长的泵浦光源达到前增益后补偿的目的,最终实现在放大器输出端信号光增益谱平坦化。通过对拉曼增益谱前后沿做线性化处理,化简稳态SRS耦合波方程的解析解,最终在输出端得到了一个固定的功率输出值。模拟结果表明:所设计的放大器具有增益平坦度好、增益高的优点,且设计方法简单。该方案为增益平坦化的拉曼光纤放大器设计提供了一种新的思路。     

波片法对Nd:YVO_4 1064nm谱线增益的控制

Nd:YVO4是一种重要的激光晶体,广泛的应用到各种激光器中,本论文着重阐述不同的偏振光对应Nd:YVO4的受激发射截面不同从而导致该谱线的增益不同,并从实验上给出了定量的结果,实验表明对于a-cut的Nd:YVO4当偏振态由π到σ变化时,受激截面由21.5×1019cm2变化到14.3×10119cm2,对应的激光输出功率也由4.1 W变化到1.7 W.利用此原理提出了一种全新的弱增益谱线与强增益谱线的和频方法,并利用此方法实现了593.5 nm激光的运转.     

基于一种优化的梳状布里渊增益谱实现对任意周期信号的零展宽快慢光

在理论分析任意信号实现无畸变快慢光所需条件的基础上,根据周期信号的频谱特点,推导出一种优化的梳状布里渊增益谱的普适公式.利用该普适公式,可根据所需时间延迟或超前量,方便地得到周期信号每个离散频谱分量所对应的各离散布里渊增益谱的强度和增益谱峰值相对于频谱分量的偏移量,从而确定整个梳状布里渊增益谱的形状.通过对正弦信号、周期性高斯信号和周期性方波信号的数值计算,结果表明,利用该优化的梳状布里渊增益谱可实现这三种周期信号在零展宽下的快慢光,证实了所得普适公式的正确性.此外,通过调节各离散布里渊增益谱的强度和偏移量,时间延迟或超前量连续可调.     

增益竞争双波长放大单频光纤放大器理论研究

引入增益竞争是抑制单频光纤放大器中受激布里渊散射(SBS)的有效方式. 在单频光纤放大器的基础上, 推导了描述增益竞争双波长放大单频掺镱双包层光纤放大器的稳态速率方程组, 建立了增益竞争双波长放大单频光纤放大器的理论模型; 利用建立的理论模型模拟分析了信号光波长间隔、 信号光种子功率比、 抽运方式和增益光纤长度等因素对放大器的单频激光输出 效率以及SBS抑制效果的影响.     

掺铒光纤放大器中抽运问题的理论分析

依据掺铒光纤放大器的速率方程和光传输方程,在不计放大自发辐射的情况下,得出了抽运功率和信号增益在放大器中沿光纤分布的隐函形式的解析表达式,并利用数值模拟对三种抽运方式下的放大器特性进行了分析。     

The amplified model of erbium-doped fiber amplifier (EDFA) with cross-phase modulation (XPM)

Based on the rate equations and the power propagation equations, the amplified model is obtained which considers the cross-phase modulation (XPM)-induced intensity fluctuation between pump power and signal power in erbium-doped fiber amplifier (EDFA). Simulation results show: a higher nonlinear coefficient and a stronger pump power cause a stronger XPM in EDFA. Before the optimal length of EDF, the intensity caused by XPM increases with the increasing length, but after the optimal length, the XPM presents saturation. A bigger nonlinear coefficient γ corresponds to a smaller optimal length and gain, and makes gain saturation more easy. XPM effect will decrease EDFA’s amplified efficiency.     

带光隔离器的掺铒光纤放大器性能分析

本文通过速率方程对带光隔离器的掺铒光纤放大器(EDFA)的性能进行了理论分析.由于光隔离器有效地抑制了反向传输的放大自发幅射(ASE),从而改善了掺铒光纤放大器的增益、噪音系数和输出功率等性能,分析结果表明光隔离器加在最佳位置时,可使小信号增益提高约5dB,噪音系数降低约1.6dB.     

线性啁啾长周期光纤光栅用作EDFA增益平坦滤波器的理论研究

提出用具有特定折射率调制包络的线性啁啾长周期光纤光栅作为掺铒光纤放大器(EDFA)的增益平坦滤波器.采用龙格库塔迭代法数值求解该类型光栅耦合模方程,就特定的掺铒光纤放大器增益谱,用Nelder-Mead优化算法对光栅结构参量(光栅长度、周期、线性啁啾系数、折射率调制包络的形状等)进行优化,设计出能在C波段35 nm带宽范围内对掺铒光纤放大器进行平坦化(增益起伏在±0.5 dB之内)的平坦滤波器.     

Modeling and optimizing of low-repetition-rate high-energy pulse amplification in high-concentration erbium-doped fiber amplifiers

Starting from the modeling of isolated ions and ion-pairs, a closed form rate and power evolution equations for pulse amplification in high-concentration erbium-doped fiber amplifiers (EDFAs) are constructed. According to the equations, the effects of ion-pairs on the performance of a high-concentration EDFA in steady state including upper-state population, ASE powers without input signal are analyzed numerically. Furthermore, the effects of ion-pairs on the dynamic characteristics of low-repetition-rate pulse amplification in the EDFA including the storied energy, output pulse energy and evolution of pulse waveform distortion are systematically studied by using the finite-difference method. The results show that the presence of the ion-pairs deteriorates amplifier performance, such as the upper-state population, ASE power, storied energy, output pulse energy, and saturated gain, etc. For the high-concentration EDFA, the optimum fiber length should be modified to achieve a better performance. The relations between the evolution of pulse waveform distortion or output pulse energy and the input pulse peak power are also discussed. The results can provide important guide for the design and optimization of the low-repetition-rate pulse amplification in high-concentration EDFAs.     

宽带喇曼/EDFA混合放大器的优化设计

采用改进的模拟退火算法对Raman/EDFA混合放大器的增益谱进行了优化,根据EDFA及Raman的功率传播方程获得了简洁的目标函数.通过对模拟退火算法几个优化环节的改进,使其能够更快速地应用于Raman/EDFA的多峰值问题的优化设计,可以在短时间内获得最优的放大器参量.计算结果表明选择合适的喇曼抽运波长和抽运功率,仅用4个反向抽运的分布式喇曼放大器加C波段的EDFA就可以获得C+L波段约70 nm的带宽、开关增益达到15 dB、最大增益波动小于1.2 dB的平坦增益谱,而且无需额外的平坦滤波器.     

A global design of an erbium-doped fiber and an erbium-doped fiber amplifier

A global design of an erbium-doped fiber and an open-loop erbium-doped fiber amplifier (EDFA) in a steady-state operation is discussed by applying genetic algorithms. Taking a signal gain and a bandwidth as objective functions, 7 parameters of the EDFA (erbium concentration, core radius, erbium-doped radius, refractive index difference, fiber length, pumping wavelength and signal power) are optimized by solving optical propagation equations, assuming a homogenous two-level active medium and a single-mode propagation. There is evidence to show that the 1480 nm pump utilized in usual EDFAs is not an optimal choice, which should be chosen around 1460 nm. The optimal core radius ranges 0.465–0.548 μm on pumping power 50–200 mW. Under different design objects and with different pumping powers, however, there are different optimal Er-doped concentrations, reflective index differences and fiber lengths. As a single fiber EDFA, 35 dB signal gain or 35 nm bandwidth is obtained with the 7 optimal parameters, 100 mW pumping power and 0.001 mW input signal power.     

Theoretical Model of Bidirectional Signal Propagation in Distributed EDFAs

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Remotely Pumped Hybrid Amplifiers for Extended Bidirectional Passive Optical Networks

In this contribution, we optimize design parameters of hybrid optical amplifiers utilizing distributed Raman amplification in transmission fiber and gain of discrete, remotely pumped erbium-doped fiber amplifier (EDFA) for wideband, bidirectional operation in metropolitan area networks (MAN). The design is based on an application of a numerical model, which takes into account pump-to-pump and signal-to-signal interactions and generation of amplified spontaneous emission in the Raman amplifier and solves the standard rate-propagation equations in an erbium-doped fiber (EDF). We predict 12 dB gain across 72 nm of optical bandwidth with gain ripple better than 10%. The recently proposed serial topology of EDFA is considered; this enables the wideband, bidirectional operation of a hybrid amplifier with only two pump laser diodes emitting in the 1430 and 1480 nm bands.     

光纤布喇格光栅作为增益均衡器的掺铒光纤EDFA放大器

采用平均反转率模型分析了带光纤布喇格光栅的增益平坦掺铒光纤放大器,其输出增益可由一组耦合超越方程描述,而非耦合微分方程,同时讨论了用于增益平坦的布喇格光栅的最佳位置设计作为增益建模和最佳设计实例,对于输入功率0.5mW位于1545～1552nm的8个波长信道,得到的输出增益不平坦度小于0.05dB.最后还证实了布喇格光栅作为增益均衡器具有高输出功率和功率转换效率的优越性.