高功率高光束质量带内泵浦皮秒放大激光系统

利用片状Nd:YVO4晶体为增益介质,研究了部分端面泵浦板条带内泵浦皮秒放大激光系统。发展了部分端面泵浦板条放大器的模式匹配方式,充分结合了带内泵浦和部分端面泵浦板条放大器二者的优势,最终实现了平均功率60.7W、脉冲宽度16.8ps、重复频率20MHz的皮秒激光放大输出,光-光转换效率达到25.3%,当放大输出功率50 W时,光束质量因子(M2)为1.55。     

1.8 mJ高倍率Nd:YAG板条皮秒激光放大器

设计了一种高倍率的固体皮秒脉冲激光放大器,采用Nd:YAG板条作为激光增益介质。借助板条结构的角度选通结构,搭建了板条五通放大系统,实现了对注入皮秒脉冲激光的高倍率放大。种子源工作在脉冲模式,放大器泵浦源在连续模式工作。皮秒光纤激光器可以在不同的重复频率下工作,脉冲宽度为13.4 ps。种子光经过隔离和耦合系统之后,注入板条的单脉冲能量为25 nJ。当种子源工作重复频率为24.46 MHz时,板条放大器输出平均功率377 W,单脉冲能量15.5 μJ;当种子源工作重复频率为49.8 kHz时,板条放大器输出平均功率89 W,单脉冲能量1.8 mJ,峰值功率为134 MW,放大倍率达到7.2×104。     

高功率超短脉冲在增益介质中的传输特性

在考虑了增益介质的群速度色散、克尔非线性效应、增益饱和和增益谱后,推导出了光脉冲在介质中的传输方程.采用分步傅里叶变换法数值模拟了高功率线性啁啾脉冲在增益介质中的传输状态,并着重讨论了增益色散对光脉冲形状和功率谱的影响.计算结果表明:当高功率超高斯光脉冲在增益介质中传输放大时,脉冲形状变得尖锐,峰值向脉冲前沿移动;功率谱峰值向低频方向移动,并且在功率谱边缘形成非对称振荡结构;当介质的增益色散增大时,光脉冲光谱宽度变窄,峰值功率减小,因此对于宽光谱脉冲,增益色散将会导致损耗.     

保偏光纤中在不同频率区域拉曼效应和参量放大增益谱

根据考虑拉曼效应后的双折射光纤所满足的非线性相干耦合薛定谔方程, 推导出了当沿两个偏振轴入射两束不同波长的激光脉冲时所产生的增益表达式. 通过与入射相同频率的光脉冲所产生增益的对比, 在考虑拉曼效应的情况下, 讨论了入射不同频率光脉冲对增益谱的影响. 结果表明, 在正常色散区和反常色散区, 当输入两束激光脉冲频率不同时, 增益谱较输入相同频率激光脉冲时产生了明显的变化, 其外侧的斯托克斯部分和反斯托克斯部分增益峰, 随着群速度失配的增加强度明显加强、偏离中心频率, 可以用于提取太赫兹脉冲.当两偏振模处于不同色散区时, 增益谱与不考虑拉曼效应时也存在明显的不同, 增益谱的对称性遭到破坏, 斯托克斯部分的增益峰强度要明显高于反斯托克斯部分. 关键词： 不同频率区域 保偏光纤 拉曼效应 参量放大     

非单色光抽运的光参量啁啾脉冲放大的带宽及增益特性研究

采用傅里叶变换的方法将脉冲光分解成不同的频率成分,建立了非单色光抽运的光参量放大耦合方程组的数值求解模型.研究了非单色抽运光对光参量啁啾脉冲放大的小信号增益、大信号增益以及增益带宽的影响.非单色抽运光降低参量放大的增益水平,但同时可提高增益带宽,且抽运光谱宽越宽,对增益带宽的提高作用越大.还进一步从相位失配和参量带宽的角度分析了非单色抽运光使参量放大的增益降低、带宽增大的原因. 关键词： 光参量啁啾脉冲放大 非单色光 增益带宽 飞秒激光     

掺钕保偏光纤放大器的研究

对掺钕双包层光纤放大器中抽运光和信号光沿光纤传播的功率分布进行了数值模拟,以808nm半导体激光器为抽运源,掺钕双包层保偏光纤为增益介质,对种子注入主振荡光纤放大器进行了理论分析和实验研究.利用实验室自制的皮秒锁模激光器为种子源,注入1064nm皮秒锁模脉冲,获得了稳定的放大脉冲.小信号时的放大倍数为300（增益为25dB）,获得了平均功率5W的皮秒脉冲.同时利用TDS5104型示波器探测信号光放大前后的波形,并用光谱分析仪得到输出脉冲激光的光谱图. 关键词： 光纤放大器 掺钕保偏光纤 种子注入 反向抽运     

包层泵浦fs光纤放大器的实验研究

 在实验上对双包层光纤放大器进行了研究。采用新型内包层为六边形的铒镱共掺双包层光纤作为放大介质,用带尾纤的半导体激光器进行泵浦,对fs光脉冲进行放大。当用2.5 W的入纤功率泵浦50 cm长的双包层铒镱光纤时,把平均功率为10.8 mW、重复频率20.84 MHz的激光放大到176 mW,增益为12.2 dB,相应的单脉冲能量为8.1 nJ,放大后脉冲宽度为480 fs,峰值功率为16 kW。     

多程放大中激光脉冲交叠放大的物理建模与计算方法

建立了多程放大中激光脉冲在增益介质中交叠放大的物理模型, 并提出相应的计算方法. 物理模型中考虑了脉冲前后沿对增益介质中反转粒子数的共同消耗. 研究认为模型在延时系下的数据递推方式无法求解交叠放大问题. 通过建立新的时空坐标系, 解决了交叠放大过程的数值求解问题. 基于此物理模型和计算方法, 模拟计算了双程放大时脉冲时间波形与腔镜位置的关系. 关键词： 物理模型 放大 腔镜 增益饱和     

高斯光脉冲在非线性增益介质中的孤子特性

本文从理论上分析了高斯光脉冲在非线性增益介质中的传播特性,从而解释高斯光脉冲的压缩及展宽和形成光孤子的机理。用计算机模拟了不同参数的高斯光脉冲在非线性增益介质中的传播过程,并获得了脉宽沿传播方向变化的定量关系。结果表明,以不同能量向增益介质中注入高斯脉冲,有可能产生各阶光孤子,但由于增益的存在,光孤子的传输距离受到限制。     

掺钛蓝宝石激光放大器中放大自发辐射效应研究

 给出了描述掺钛蓝宝石激光放大器的速率方程组，通过对放大介质内反转粒子数密度和放大自发辐射的时间和空间特性的数值计算与分析，提出可通过控制泵浦光脉冲和信号光之间的时间延迟来有效地抑制放大自发辐射对放大器增益的影响。     

Study of nonlinear propagation of chirped optical pulses in laser amplifying medium

In chirped pulse amplification, the amplification of an optical pulse in laser amplifying medium is a very important link. After considering dispersion, Kerr nonlinear effect, gain distribution and loss of the medium, the physical model that the optical pulse propagates in the medium has been established, which is suitable for the general situation where the optical pulse propagates in the amplifying medium. Using a split-step Fourier method, the propagation state of a chirped optical pulse in the amplifying medium has been numerically simulated, and the influences of the gain dispersion of the medium and the frequency detuning of the pulse on the optical pulse have been discussed emphatically. The results show that, with the amplification and propagation of the ultrashort chirped pulse in the amplifying medium, gain saturation and Kerr nonlinear effect of the medium will cause distortion of the optical pulse. For the optical pulse with a wideband spectrum, gain dispersion will cause the gain narrowing effect, so it is equivalent to a loss mechanism. The frequency detuning of the optical pulse will cause distortion of the pulse, which can be used to weaken the impact of gain saturation, thus reshaping the optical pulse.     

A computational theory of short pulse generation

The semi-classical equations for the electric field and population inversion in a two-level medium are simplified for the case of a saturable absorber cell which is shorter than the length of fluctuations in the optical-pulse envelope. The spatial coordinates in the cell are effectively lumped, and the integration is reduced to the one dimension of time. The pulse is passed through an amplifying medium and frequency selective elements by a fast Fourier transform into its spectral components. The case of pulse formation in a ruby laser, starting from a noise fluctuation is computed for the parameters of a recently reported accurate measurement of pulse duration. Good agreement is obtained with experiment. Finally, a pulse length is predicted for a cavity containing an etalon which cancels gain narrowing.     

介质参数对KrF激光放大器的影响

本文对对KrF激光产生的动力学过程及发光机制进行了研究,利用激发态二能级稳定态理沦,得到了介质的增益、饱和光强以及腔内最佳光强随介质成分和压强的依赖关系,可以作为准分子激光器介质参数选择的依据.并介绍一种用Goblin装置放大短脉冲的方法.     

Frequency dependence of amplifying parameters of a copper vapor laser using air as a buffer gas

We use a pair of copper vapor lasers in an oscillator–amplifier configuration to investigate amplifying parameters such as the small signal gain and the saturation intensity versus the pulse repetition frequency when two different types of buffer gases are employed. We show that the values of these parameters are not the same if different gas mixtures are used in the gain medium. We show that the values of the parameters are estimated to be higher if a He–Ne buffer gas is used than in the case of air. The laser output power is relatively high and has fairly good stability at some special pulse repetition frequencies when air is used as a buffer gas.     

高功率激光放大器中光束的成丝和B积分

研究了高功率激光放大器中光束的成丝问题,利用弗兰兹－诺德威克（Frantz-Nodvik)模型将准稳态波动议程推广到介质有饱和增益的情形,进而得到高功率激光放大器中小尺度调制的传输方程,在小信号增益和饱和增益情形下,分别得到了小尺度调制方程的精确解析解和数值解。结果表明,对于相同的输入光强,增益使小尺度调制增益谱的范围加宽,最快增长频率增高,最大增长率提高;同时,在放大介质中,小尺度调制的最快增长频率和最大增长率还随传输距离变化,增益饱和效应使小尺度调制的增长速度以及B积分的增长低于无饱和放大情形。     

Phase-modulation effects in synchronously pumped dye lasers

We report the numerical calculation of pulse generation in SPDL including phase-modulation effects due to gain saturation. The steady-state pulses are strongly down-chirped at the leading edge if the laser frequency is detuned from the line centre of the amplifying dye. The pulse duration is found to be almost independent of wavelength detuning.     

高功率LDA紧密环绕抽运Nd:YLF放大器实验研究

 采用高功率LDA紧密环绕抽运10mm×10mm Nd:YLF和两级双程离轴行波放大结构，实现了对5mm×5mm口径激光的放大。分析并实验研究了在不同抽运电流及不同抽运延时条件下，激光放大器及两级双程离轴放大系统小信号增益的规律。实验得到两级双程放大系统的小信号净增益可达600。     

56 MHz重复频率端泵SESAM连续波锁模Nd∶YVO4激光器

为了增大皮秒注入种子激光的能量,获得较高的激光放大效率和信噪比,关键是要在保持较高的平均锁模激光功率下实现连续波锁模激光器的低重复频率运转。通过选取五镜折叠激光谐振腔腔型和参数设计,克服了随着腔长增加损耗加大而导致的激光锁模不稳定的困难。分析了较长腔长条件下工作物质和SESAM光斑尺寸的大小和变化,及其对激光器稳定性的影响。由于SESAM饱和工作和稳态条件的能量要求,在激光谐振腔调整过程中,对应臂长的光程互补变化。实验中采取腔长和晶体热控制方式,优化了激光谐振腔的工作参数,实现了脉冲能量10.7 nJ,重复频率56 MHz,平均功率1.2 W的SESAM连续波锁模激光输出。     

Dissipative soliton resonance in a passively mode-locked fiber laser

The phenomenon of dissipative soliton resonance (DSR) predicts that an increase of pulse energy by orders of magnitude can be obtained in laser oscillators. Here, we prove that DSR is achievable in a realistic ring laser cavity using nonlinear polarization evolution as the mode-locking mechanism, whose nonlinear transmission function is adjusted through a set of waveplates and a passive polarizer. The governing model accounts explicitly for the arbitrary orientations of the waveplates and the polarizer, as well as the gain saturation in the amplifying medium. It is shown that DSR is achievable with realistic laser settings. Our findings provide an excellent design tool for optimizing the mode-locking performance and the enhancement of energy delivered per pulse by orders of magnitude.     

Quelques propriétés optiques du laser tunnel

The cw oscillation of a tunnel laser is demonstrated. The high losses encountered in tunneling systems are here compensated for by a high gain amplifying medium for barrier widths between 0 and λ/2. For a first particular angle of incidence, the TM frequency remains invariant when the total length of the laser is varied. For a higher value of the incidence angle, the frequency associated with the TE polarization increases while the frequency associated with the TM polarization undergoes a negative variation when the total length of the laser is reduced.