双波长飞秒激光器量子理论研究

本文建立了一个不涉及具体光腔结构的双波长固体飞秒激光器模型,分析了群达弥散(GVD)、自相位调制(SPM)、交叉耦合、损耗调制和增益放大的动态平衡过程.从场算符的定义出发,导出了双波长飞秒激光器的量子锁模方程组,并且将该量子销模方程组化为经典锁模方程组.结果表明,该方程组和非线性薛定谔方程有着类似的结构,方程组存在稳定的脉冲解,因而从理论上证明了双波长飞秒激光器可以实现双波长同时锁模.     

双波长飞秒激光器锁模动力学的数值分析

采用有限发方法对双波长飞秒激光器的锁模方程进行了数值分析,得到了不同参数交叉锁模脉冲的数值解。结果表明,在双光束谐振腔内,由于自相位调制、群速色散、交叉耦合、增益放大以及损耗调制的作用,在一定条件下,激光器能够从连续运转状态发展到锁模状态,并产生双波长飞秒交叉锁模脉冲。     

利用SBR实现自启动锁模钛宝石飞秒激光脉冲的产生

利用国内生长的低损耗双量子阱结构的可饱和布拉格反射器在掺钛蓝宝石激光器中实现了可饱和吸收体被动锁模、孤子锁模和KLM锁模状态的自启动稳定运转.当抽运功率为4.5W时，用啁啾镜进行色散补偿，获得了18fs的KLM锁模脉冲，输出功率为150mW. 关键词： 可饱和布拉格反射器 啁啾镜 飞秒 钛宝石激光器     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

钛宝石飞秒激光振荡器的稳定性改善

对钛宝石飞秒激光器脉冲序列的强度和时间的稳定性进行了分析.实验比较了钛宝石飞秒激光器底板有无水冷的条件下,输出锁模脉冲序列的稳定性以及中心波长和光谱宽度的变化.结果表明对钛宝石飞秒激光器底板施加水冷可改善锁模脉冲的稳定性. 关键词： 钛宝石激光器 稳定性 飞秒脉冲     

同步泵浦PML飞秒激光研究

采用CW锁模YAG倍频激光器同步泵浦PML飞秒染料激光器,产生了平均脉宽约55fs、功率为15mW的光脉冲。文章在理论和实验上还研究了同步泵浦飞秒激光脉冲产生技术。     

飞秒被动锁模环形腔掺Er3＋光纤激光器

在考虑增益、损耗、群速度色散、自相位调制、快速可饱和吸收体等各种参数同时作用情况下，分析了非线性偏振旋转效应自启动锁模机理，研究了腔体参数与锁模脉冲之间的关系，并给出飞秒被动锁模环形腔掺Er3＋光纤激光器实验原理。实验采用性能稳定的980nm半导体激光器作为抽运源，高掺杂短长度掺Er3＋光纤作为增益介质，利用非线性偏振旋转锁模技术，得到了稳定的飞秒自起振锁模光脉冲。抽运功率为23mW时，激光器输出锁模脉冲中心波长1552nm，3dB带宽为7.6nm，重复频率14.0MHz，平均输出功率0.43mW，自起振锁模泵浦阈值功率11.5mW,并观测到了稳定的高阶锁模脉冲输出。该激光器与报道过的相同结构光纤激光器相比,自起振泵浦阈值低、脉冲能量高、稳定性好，且频谱边带幅度小。     

303MHz高重复频率掺Er光纤飞秒激光器

高重复频率掺Er光纤飞秒激光器在光学频率梳、超高速光学采样等领域具有很重要的作用. 本文采用非线性偏振旋转锁模机理, 在掺Er光纤飞秒激光器中实现了重复频率为303 MHz的锁模脉冲输出. 通过优化腔内色散, 激光器腔内色散在零色散附近偏负值, 锁模后工作在展宽脉冲锁模状态. 在817 mW抽运功率下, 激光器在连续光状态下可以输出125 mW的平均功率, 在锁模状态下可以输出69 mW的平均功率, 脉冲宽度为90 fs. 当抽运功率处于700-817 mW时, 激光器可以实现自启动锁模. 激光器重复频率在5 h内的漂移量为30 Hz.     

对撞脉冲锁模Nd:YAG激光器的实验研究

本文报道了对撞脉冲锁模Nd:YAG激光器的实验装置,试验了影响对撞脉冲锁模激光器性能的各种参量.在最佳参量运转时获得了最短的脉宽为8ps,输出能量的稳定性～±7%.     

高稳定性、高质量脉冲压缩飞秒光纤激光系统研究

报道了一款用于眼科手术的高稳定性、高质量脉冲压缩飞秒光纤主振荡功率放大系统. 振荡器采用混合腔方式增加了光纤双折射, 改善了非线性偏振旋转锁模在低重复频率下无法自启动的缺点, 提高了飞秒光纤激光器自启动锁模的稳定性. 研究了脉冲预啁啾与飞秒脉冲压缩质量的关系, 通过实验证明了光纤放大器的入射脉冲保持负的预啁啾状态可以得到最好的脉冲压缩结果. 实验最终实现了满足自启动锁模条件的重复频率19.4 MHz、平均功率1.2 W、脉冲宽度183 fs的激光脉冲, 目前这台激光器是国内首台具有自主知识产权并应用于动物角膜实验的飞秒光纤激光器.     

Investigation of self-focusing a Gaussian laser pulse in a weakly relativistic and ponderomotive regime inside a collisionless warm quantum plasma

This article investigates nonlinear self-focusing of an intense right hand circularly polarized Gaussian profile laser pulse in a weakly relativistic and ponderomotive regime inside a collisionless and unmagnetized warm quantum plasma. The nonlinear propagation equation for laser pulse in plasma has been derived. Then, the evolution differential equation for laser spot-size was obtained with considering the parabolic equation approach under the Wentzel-Kramers-Brillouin and paraxial ray approximations. This differential equation was solved numerically by fourth-order Runge-Kutta method. It is shown that our solution confirms the results of the self-focusing of the laser pulse in a weakly relativistic ponderomotive regime in cold quantum plasma in extreme conditions. Numerical results indicate that self-focusing of the laser pulse in the presence of relativistic and ponderomotive nonlinearity inside warm quantum plasma is improved in comparison with relativistic and ponderomotive cold quantum plasma.     

Propagation of the ultrashort laser pulses through the quantum nonlinear medium with resonant properties

The propagation of ultrashort few-cycle laser pulses through a quantum nonlinear medium with resonant properties is studied using the method of slowly varying amplitudes with allowance for dispersion effects. A self-consistent system of nonlinear wave equation for the evolution of laser field and the nonstationary Schrödinger equation that determines the material polarization response is numerically solved. Specific features of the propagation of laser pulse caused by a relatively large spectral width and the nonadiabatic character of the laser pulse are established. The rise of the slowly dumping polarization at the eigenfrequency of the medium and the consequent stretching of the laser pulse are observed. The role of the resonant absorption of the laser energy in the medium is analyzed. The nonlinear spectral broadening is demonstrated for the laser pulse propagating through the medium.     

Ionization and population transfer in lithium Rydberg states with ultrashort chirped laser pulses

We present a theoretical study of dynamics of Rydberg states of lithium using ultra short chirped laser pulse having a Gaussian envelope. The population transfer probabilities are calculated of different Rydberg states on chirped laser factors. The calculations are performed by direct numerical integration of Schr?dinger equation using fourth order Runge-Kutta method. The behavior of dynamics of Rydberg states for these factors is of great significance. These results are of potential interest in coherent quantum control, quantum computation and in many physical and chemical processes.     

Tracking individual electron trajectories in a high harmonic spectrum

The harmonic spectrum generated by a few-cycle laser pulse propagating through a gas jet is calculated. Two complementary atomic response models are used, one based on the time-dependent Schrödinger equation and the other on quantum orbits in which only a single pair of electron trajectories are taken into account. The role played by individual electron trajectories in determining particular features of the spectrum are considered and phase-matching maps are used to help understand their structure. A method based on this connection is proposed for diagnosing the carrier-envelope phase and the pulse duration of the incident laser field.     

电子等离子体波对超短脉冲激光传播过程的作用

提出等离子体波对光脉冲产生相位调制的观点,把光脉冲在背景等离子体波中传播时的频率移动与脉宽压缩效应统一起来。给出了脉宽演化的方程,它类似于在势阱中运动的经典粒子的能量守恒方程;估算了脉宽压缩对应的等离子体波振幅阈值。数值计算进一步证实这些结论。最后指出实验上用等离子体波压缩短脉冲激光脉宽的可能性。 关键词：     

Sm2+掺杂的无机光谱烧孔材料量子效率研究

本文由光谱烧孔的发光动力学方程出发,推导了脉冲光烧孔并选通的情况下量子效率的表达式.在77K下测量了以不同功率的560nm脉冲光烧孔并选通的条件下,孔深随烧孔脉冲数目的变化,验证了烧孔的量子效率与选通光强度的关系.在相同的烧孔条件下测量了BaF(Cl,Br):Sm²⁺与SrF(Cl,Br):Sm²⁺的孔深随脉冲数目的变化,验证了量子效率与⁵D_J-⁷F₀跃迁几率的关系.     

Numerical modeling of the photoionization of Rydberg atoms by the field of an electromagnetic wave

The ionization of excited hydrogen-like atoms in a femtosecond laser pulse is studied by direct numerical integration of the time-dependent Schrödinger equation for a quantum system in the field of an electromagnetic wave. Expressions are obtained for the ionization probability of the system as a function of the parameters of the laser pulse and the initial state of the atom. Ionization suppression is found, confirming the basic premises of the theory of interference stabilization of Rydberg atoms.     

Generation of XUV attosecond pulses in the process of atomic ionization by few-cycle laser radiation

Ionization of a model two-electron atom in the presence of a strong field of ultrashort laser pulses is investigated using the numerical integration of the nonstationary Schrödinger equation, which describes the dynamics of a quantum system in the presence of an electromagnetic wave. The features of two-electron ionization in the presence of one-and two-cycle pulses are analyzed. The suppression of double ionization in the presence of ultrashort laser pulses related to a finite-time interelectron energy exchange upon the laser action is demonstrated. The features of the generation of high-order harmonics and single XUV attosecond pulses are studied for the atomic ionization by few-cycle laser pulses. The parameters of the laser pulse are optimized for the effective generation of a single XUV attosecond pulse.     

同步泵浦飞秒激光锁模理论研究

考虑到饱和增益、饱和吸收、群速弥散和自相位调制等效应对光脉冲的作用,我们给出了一个适用于飞秒脉冲激光系统的锁模方程。并且用这个方程初步地研究了同步泵浦被动锁模的染料激光器。结果表明,染料光脉冲的输出特性将极大地取决于腔内色散、S参数、饱和吸收体的浓度、腔长失谐量等因素。