利用双色啁啾激光场产生超短的单个阿秒脉冲

数值研究了氦原子在两束啁啾激光场形成的组合场驱动下所发射高次谐波的特点.计算结果表明,当两束啁啾激光场的形式为δi(t)=-βiωit2/T (i=1,2)并且啁啾参数分别为β1=0.3和β2=0.6时,高次谐波谱的平台区域能得到很大的扩展,随后通过激光场强度以及相位的优化,谐波截至能量延伸到了812eV.最后通过叠加谐波次数从160次到210次,210次到260次,260次到310次,可获得一系列脉宽为33as的单个阿秒脉冲.     

基于脉冲对的交叉相位调制脉冲压缩中离散效应的抑制

提出一种新的抑制离散效应的方法——非对称脉冲对法，并对采用该方法和采用非同步耦合法在基于脉冲对交叉相位调制对脉冲进行压缩过程中，对离散效应影响的抑制效果进行了研究.数值模拟的结果显示：对于峰值功率为10mW、半极大全宽度为5ps的高斯入射脉冲，采用非对称脉冲对法，可以获得压缩比为137、基座能量比为0122、峰值功率为116mW的压缩脉冲. 关键词： 交叉相位调制 离散效应 非同步耦合法 非对称脉冲对法     

基于耗散孤子种子的啁啾脉冲光纤放大系统输出特性

以不同滤波器带宽下获得的全正色散光纤激光器耗散孤子作为啁啾脉冲放大(CPA)系统的种子脉冲, 研究了光栅对和光纤展宽器CPA系统输出脉冲的可压缩性. 结果表明, 对于大能量耗散孤子种子脉冲, 当CPA系统采用正色散光纤展宽器时, 光纤群速色散与自相位调制之间的相互作用不仅可抑制耗散孤子脉冲光谱调制的影响, 还可使脉冲在光纤展宽器中自相似演化, 从而可提高CPA输出脉冲的可压缩性. 通过优化光纤展宽器长度, 对于耗散孤子种子源, 采用光纤展宽器的CPA系统输出脉冲可压缩性与主脉冲所占脉冲总能量之比均优于采用光栅对展宽器时的情况.     

采用组合脉冲驱动生成单一的X射线阿秒脉冲

采用组合激光脉冲(800 nm/9.4 fs 24 nm/1 fs)辐照联合两原子体系产生高次谐波,获得了单一的X-射线阿秒脉冲.我们发现,当固定钛宝石激光的峰值强度并改变高频谐波脉冲的峰值强度Ih时,存在一个优选的Ih范围,在该范围内相应的阿秒脉冲最优化,即强度达到最强,对此,本文从受激复合的角度给出了合理解释.     

基于脉冲变压器和脉冲形成网络的高压脉冲源北大核心CSCD

为了满足在高电压状态下对氧化锌陶瓷（ZnO）元件的检测需要,研制了一种基于脉冲变压器和脉冲形成网络（PFN）的,输出电压范围10-80kV可调,波形为近方波的高压脉冲源。根据实际研制过程,分别介绍了高压脉冲源的设计、仿真及系统电路构建。测试了高压脉冲源在标准负载（匹配）和氧化锌陶瓷负载上的输出情况。结果显示：脉冲顶降小于3%,顶部波动小于1.5%,前后沿指标均满足要求。因而,高压脉冲源可以用于氧化锌陶瓷的性能检测。     

Generalizations of the short pulse equation

We classify integrable scalar polynomial partial differential equations of second order generalizing the short pulse equation.     

Limit for pulse compression by pulse splitting

We have detected a fundamental pulse-compression limit for high-nonlinear fibers in the normal dispersion regime near the zero-dispersion wavelength. The desired generation of a broadband continuum by self-phase modulation is limited by already small amounts of third-order dispersion (TOD), which results in pulse splitting above a critical pulse power. We investigate the critical fiber length in dependence on pulse- and fiber parameters.     

KrF激光脉冲整形研究

 实验研究了脉冲堆积法对KrF激光的整形能力。利用受激布里渊散射(SBS)压缩脉冲获得了脉宽为3~5 ns的短脉冲，用4束激光堆积获得了脉宽为10~15 ns、平顶宽度为5~10 ns的整形脉冲。利用实测SBS脉冲数据，对脉冲堆积法进行了数值模拟，模拟的脉冲宽度为12.7 ns，平顶宽度为7.7 ns，该结果与实验相符。对脉冲堆积法的任意整形能力进行了模拟，讨论了脉冲宽度变化对整形的影响，发现脉宽变化在5%以内时，对整形脉冲的影响较小。对整形脉冲的放大进行了定性研究，结果表明：平顶脉冲通过放大器后，前沿部分放大较多，由于饱和作用，后沿放大较少；如果前端整形脉冲前沿为斜坡状，放大后可以得到近平顶的脉冲。     

利用脉冲负反馈压缩准分子激光脉冲

 分析了准分子激光脉冲在放大过程中的展宽现象。将饱和开关技术应用于放电泵浦激光器放大腔的放大压缩,发展了脉冲负反馈饱和压缩技术。利用该技术在天光一号系统前端LPX-150激光器上成功获得能量100 mJ、脉宽10 ns的脉冲输出,其空间分布均匀性保持在3%以内。这证明该技术可与无阶梯诱导非相干技术联合使用,在保证光束均匀性基础上进行脉冲压缩。     

Conservation laws of the complex short pulse equation and coupled complex short pulse equations

In this paper, the complex short pulse equation and the coupled complex short pulse equations that can describe the ultra-short pulse propagation in optical fibers are investigated. The two complex nonlinear models are turned into multi-component real models by proper transformations. Lie symmetries are obtained via the classical Lie group method, and the results for the coupled complex short pulse equations contain the existing results as particular cases. Based on the linearizing operator and adjoint linearizing operator for the two real systems, adjoint symmetries can be obtained. Explicit conservation laws are constructed using the symmetry/adjoint symmetry pair (SA) method. Relationships between the nonlinear self-adjointness method and the SA method are investigated.     

Linking NMR pulse sequences: derivative relation between the responses of two pulse sequences

Examples are shown of how the derivative of the response of an NMR pulse sequence with respect to a variable in that pulse sequence can be obtained by another pulse sequence. This approach holds the potential of being a tool for discovery of new pulse sequences or a means of understanding how some pulse sequences are related to each other.     

Dependence of the pressure pulse generated in an opticoacoustical receiver on the intensity of the exciting laser pulse

Calculations of the time form and amplitude of the acoustic signal generated in an absorbing gas that fills the cuvette of an opticoacoustical receiver in the case of a nonlinear nonsteady interaction with a single laser pulse are performed. Expressions relating the parameters of the acoustic signal with the characteristics of the laser pulse are derived, and an expression is proposed for the parameter characterizing the nonlinearity of the absorption of the given gas.     

Effect of pulse parameters on the passive layer formation on pulse plated Ni-Co alloys

From a chloride bath, Ni-Co alloys were pulse plated by varying the pulse parameters off-time and the peak current densities using a pulse generator that applies a square wave signal in order to examine the mechanism of the passive oxide layer formation on the deposited coatings in the frame of pulse parameters.Cyclic voltammetry and potential step measurements were carried out in order to characterise the electrochemical behaviour on the Ni-Co coatings at a selected electrode potential in an alkaline solution. Calculation of the oxide layer formation was evaluated from the total charge, determined by recorded current-time transients and from ICP-analysis of the samples. The most protective and compact oxide was formed on the sample that was deposited at low current densities and at high off-time.     

Extremum conditions for the radiation pulse energy and efficiency of a pulse gas-discharge laser

The case of incomplete similarity for which the processes in pulse gas-discharge lasers (PGL) are only similar in time is examined theoretically. It is shown that this kind of similarity is realized in PGL upon attainment of maximum efficiency. Theoretical computations are compared with experimental results on copper vapor PGL.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 17–21, August, 1987.The author is grateful to V. K. Konyukhov, A. A. Isaev, and G. Yu. Lemmerman for attention and useful discussions of the results.     

高阶效应对超短艾里-高斯脉冲相互作用的影响

本文运用分步傅里叶变换,对满足高阶耦合非线性薛定谔方程的超短艾里脉冲与超短高斯脉冲,利用MATLAB数值模拟了在高阶效应下两脉冲相互作用后的演化过程以及时域上的强度变化.获得了负三阶色散效应使超短脉冲相互作用能传输更远距离;正三阶色散效应会减慢超短脉冲相互作用的传输.自陡峭效应通过孤子分裂现象的形式使超短脉冲相互作用产生时域位移.内拉曼效应可以将超短脉冲相互作用的能量由前沿处转移到后沿处.     

高阶效应对超短艾里-高斯脉冲相互作用的影响

本文运用分步傅里叶变换,对满足高阶耦合非线性薛定谔方程的超短艾里脉冲与超短高斯脉冲,利用MATLAB数值模拟了在高阶效应下两脉冲相互作用后的演化过程以及时域上的强度变化。结果表明：负三阶色散效应使超短脉冲相互作用能传输更远距离;正三阶色散效应会减慢超短脉冲相互作用的传输。自陡峭效应通过孤子分裂现象的形式使超短脉冲相互作用产生时域位移,内拉曼效应可以将超短脉冲相互作用的能量由前沿处转移到后沿处。     

高阶效应对超短艾里-高斯脉冲相互作用的影响

本文运用分步傅里叶变换,对满足高阶耦合非线性薛定谔方程的超短艾里脉冲与超短高斯脉冲,利用MATLAB数值模拟了在高阶效应下两脉冲相互作用后的演化过程以及时域上的强度变化。结果表明：负三阶色散效应使超短脉冲相互作用能传输更远距离;正三阶色散效应会减慢超短脉冲相互作用的传输。自陡峭效应通过孤子分裂现象的形式使超短脉冲相互作用产生时域位移,内拉曼效应可以将超短脉冲相互作用的能量由前沿处转移到后沿处。     

脉冲功率装置的脉冲形成单元研究

 介绍了所研制的脉冲功率装置的组成、脉冲形成单元的设计以及脉冲形成单元实验研究结果。研究了包含脉冲形成线的绝缘设计校验、装置的脉冲形成单元的抖动及其与主同步开关击穿延迟时间的抖动和脉冲输出开关的抖动的关系。实验结果表明：在3.6 MV脉冲电压作用下，脉冲形成线的前后尼龙隔板未出现表面闪络等绝缘问题，脉冲形成线的绝缘满足设计要求。主同步开关的抖动1.6 ns，脉冲输出开关的抖动小于3.1 ns，脉冲形成单元的整体抖动小于3.0 ns，满足装置同步性能要求。     

Scattering-induced changes in the temporal coherence length and the pulse duration of a partially coherent plane-wave pulse

The scattering of a partially coherent plane-wave pulse on a Gaussian-correlated, quasi-homogeneous random medium is investigated. The analytical expressions for the temporal coherence length and the pulse duration of the scattered field are derived. We demonstrate that the scattering-induced changes in the temporal coherence length and the pulse duration may be used to determine the correlation function of the scattering potential of the medium.     

双色激光脉冲辐照下38 as孤立短脉冲的产生

通过数值求解一维含时薛定谔方程, 本文研究了具有特定波长的双色激光脉冲与氦原子相互作用产生的高次谐波和阿秒脉冲, 这里双色激光脉冲由5 fs较低强度基频钛宝石主脉冲与另一束较高强度的1330 nm 红外附加脉冲构成. 研究发现, 若两束脉冲之间的相对相位选择合适, 可以获得宽带连续辐射的高次谐波谱, 叠加该连续辐射谱可获得脉宽为38 as的孤立短脉冲. 进一步研究发现, 不同于以往孤立阿秒脉冲研究中选出长、短量子路径之一作为辐射源, 这里单阿秒脉冲来源于长、短两个量子路径的贡献, 只是这两个量子路径在很宽的谐波次数变化范围内辐射时刻比较集中. 关键词： 双色激光脉冲 阿秒脉冲 量子路径