飞秒强激光能量在Ar原子团簇中的沉积

飞秒强激光与团簇的相互作用是一个十分活跃的研究领域,本文采用一种新的理论模型,研究了飞秒激光在团簇中的传输的过程,计算了Ar原子团簇对超强激光能量的吸收,并通过解析计算连续曲折射程、最大穿透深度和特征时间三个重要的物理参量来重新估算了这一模型的可行性.     

吡啶团簇的多光子电离和离解研究

利用飞秒激光和飞行时间质谱结合从头计算对吡啶团簇的多光子电离和离解进行了研究. 给出了吡啶团簇的稳定结构和簇内的质子转移过程.     

飞秒激光氘团簇库仑爆炸引发核聚变的机理研究

在超强飞秒激光与氘团簇的相互作用中，利用库仑爆炸模型，分析了可以引发核聚变的高能氘核产生的机理，提出了氘离子团簇膨胀尺寸与时间的关系式，计算了多种尺寸的氘团簇库仑爆炸时氘核的动能以及氘团簇的解体时间． 关键词： 飞秒强激光 氘团簇 库仑爆炸 核聚变     

Ar原子团簇与飞秒强激光相互作用产生的高能离子计算

利用改进的“等离子体球”模型模拟了Ar原子团簇与飞秒强激光相互作用的物理过程.改进后的模型弱化了原模型在共振吸收附近团簇内部屏蔽电场的异常增强行为，从而使其更为合理，计算得到的Ar离子平均动能与以往的实验结果符合.还定量地研究了Ar离子平均动能及其平均电荷态与团簇尺寸以及激光参数之间的变化关系. 关键词： 团簇 飞秒激光 高能离子 共振吸收     

原子团簇对飞秒激光的吸收

使用800nm飞秒脉冲激光研究了Xe,Ar,He等原子团簇对激光的吸收.实验结果表明,脉冲阀门的工作压力、所使用的气体种类等因素对团簇的尺寸及团簇对激光的吸收影响很大.在阀门工作压力为20×10⁵Pa、激光功率密度为1×10¹⁵W/cm²的条件下,Xe团簇对激光的吸收高达45%.激光预脉冲的存在会降低原子团簇对激光能量的吸收.离子能量测量结果表明,团簇对激光的高效吸收导致较高离子温度等离子体的生 关键词： 原子团簇 飞秒激光 能量吸收效率 高能离子     

超短超强激光及微团簇与大尺度团簇相互作用

用2.5 MV静电加器提供的高品质微团簇束与固体、气体和大尺度团簇(100->1000原子/团簇)碰撞,超强飞秒激光与大尺度氘团簇相互作用,研究微团簇在大尺度团簇中的库仑爆炸特性,研究超短超强激光场中大尺度氘团簇的聚变机理.本文将介绍此项实验研究的进展.     

氢团簇在飞秒强激光场中的动力学行为

利用分子动力学方法研究了氢团簇在飞秒强激光场中的动力学行为. 与库仑爆炸模型所预言的不同, 团簇的膨胀是各向异性的, 质子平均动能沿激光场极化方向上的分量要明显大于垂直于激光场极化方向上的分量. 讨论了团簇各向异性膨胀产生的原因, 分析了激光和团簇参数对各向异性程度的影响.     

飞秒激光氘团簇聚变

简要介绍了原子团簇的产生方法和特点以及激光惯性约束核聚变的基本原理,氚团簇在飞秒激光的作用下,大量吸收激光能量,产生了高离化态高能离子,从而实现了氚团簇桌面台式聚变。     

低密度大尺寸团簇形成的诊断研究

利用线性啁啾散射光谱测量法,研究了背压对团簇尺寸的影响以及团簇形成过程中尺寸的变化过程. 同时发现低密度大尺寸团簇的形成,可以作为相关实验需要的干净且重要的团簇靶. 关键词： 团簇 飞秒强激光 尺寸测量 线性啁啾光谱散射     

基于旋转相干光谱的整形飞秒激光转动动力学调控

我们实验上发展了基于飞秒激光旋转相干光谱的整形飞秒激光转动动力学调控方法,通过脉冲整形技术调控激发脉冲的光谱相位,从而实现对飞秒激光作用下转动态相干激发过程中复原信号及转动布居数的调控. 研究了飞秒激光旋转相干光谱对激光频谱相位的响应机制,突出了飞秒激光频谱相位在气相分子转动态相干激发中的重要作用. 为飞秒激光作用下生物大分子和团簇鉴别及结构探测研究提供了新的参考.     

飞秒激光烧蚀金属靶的冲击温度

在明确飞秒激光与物质相互作用过程冲击温度概念的基础上, 讨论了飞秒激光烧蚀铝靶和铜靶过程中的冲击温度与其他物理量的关系, 利用飞秒激光烧蚀金属的双温模型提取了冲击温度的绝对值, 基于非傅里叶热传导模型计算了冲击温度的分布. 此项研究结果对飞秒激光安全加工含能材料有借鉴意义. 关键词： 飞秒激光 含能材料 烧蚀 冲击温度     

飞秒激光脉冲与金属光阴极相互作用

本文从理论上分析了飞秒激光与光阴极相互作用过程，采用双温模型分析了飞秒激光脉冲辐照下金属薄膜的温度效应。通过建立一个简单的光电效应模型，获得了最佳的金属光阴极厚度，通过该模型可以发现，产生的光电流对在飞秒激光脉冲辐照下的电子温度和晶格温度有着很大的依赖关系。     

Interference model of femtosecond laser pulse conical emission in dispersive medium

A simple interference model is proposed for conical emission frequency-angular spectrum formation during the filamentation of femtosecond laser pulse in a nonlinear dispersive medium. The model allows to obtain analytical expressions for frequency-angular distributions of the supercontinuum spectral components of pulses at different wavelengths in media with arbitrary material dispersion law. The model reproduces the supercontinuum frequency-angular spectrum transformation for the case of laser pulse splitting into several subpulses and for multiple refocusing of the light field in filament. Frequency-angular spectra analytically calculated from the proposed interference model are in good agreement with the results of numerical simulations performed for the filamentation of femtosecond laser pulses in fused silica.     

Interaction of intense laser pulses with hydrogen atomic clusters

The interaction between intense femtosecond laser pulses and hydrogen atomic clusters is studied by a simplified Coulomb explosion model. The dependences of average proton kinetic energy on cluster size, pulse duration, laser intensity and wavelength are studied respectively. The calculated results indicate that the irradiation of a femtosecond laser of longer wavelength on hydrogen atomic clusters may be a simple, economical way to produce highly kinetic hydrogen ions. The phenomenon suggests that the irradiation of femtosecond laser of longer wavelength on deuterium atomic clusters may be easier than that of shorter wavelength to drive nuclear fusion reactions. The product of the laser intensity and the squared laser wavelength needed to make proton energy saturated as a function of the squared cluster radius is also investigated. The proton energy distribution calculated is also shown and compared with the experimental data. Our results are in agreement with the experimental results fairly well.     

An analysis of As_2S_3 chirped fiber grating formed by two-photon absorption effect

When femtosecond laser pulses interfere with chirped femtosecond laser pulses in As2S3 fiber, a chirped fiber grating is formed. An analytical expression is given to describe the chirped grating, and its Bragg reflectivity is calculated. Because of the high photosensitive effect of As2S3 material, the chirped fiber grating has a wide Bragg reflective spectrum and high reflectivity by choosing proper parameters. This indicates that the chirped fiber grating can be used as a stretcher in the femtosecond chirped pulse amplification (CPA) system.     

BBO晶体中飞秒脉冲的二次和三次谐波振荡产生

同时考察了群速色散失配、最低阶群速色散和二阶群速色散。研究了在ＢＢＯ晶体中飞秒激光脉冲的谐产生，计算了ＢＢＯ晶体的作为波长函数的晶体的最低阶和二谐群速色散，借助求解改进的耦合波方程的数值计算，得到了飞秒脉冲的二次及三次谐波辐射，分析了最低工阶及二阶ＧＶＤ对于基波脉冲和谐波脉的影响，最后考虑了三次谐波产生中群速失配的补偿。     

BEPCII横向束流反馈系统的梳状滤波器

BEPCII是一个多束团、大流强的装置, 由于高频腔的高次模和电阻壁阻抗等因素，不可避免地会出现束流不稳定性。BEPCII中采用束流反馈系统来抑制束流不稳定性。横向束流反馈系统主要包括前端电子学、信号处理电子学、反馈器件和放大器等几个部分。梳状滤波器是信号处理电子学的重要部件，利用两根长短不同的电缆以及一个功分器和合成器构成了一种简单有效的梳状滤波器，其梳状深度达到-41 dB，使用这种梳状滤波器的横向反馈系统成功地抑制了束流中出现的不稳定性。     

Threshold fluence for domain reversal directly induced by femtosecond laser in lithium niobate

Fabricating domain reversal directly induced by femtosecond laser is a novel and promising method to induce micron-period or even submicron-period inverted domain structure for it averts the domain spreading and mergence which is hard to avoid by traditional electric-field poling method. In this paper, the domain reversal process in lithium niobate crystal by irradiation of femtosecond pulses whose spatial and temporal distributions are taken into consideration is numerically simulated in the framework of Fahy’s model. The simulation results manifest the domain inversion window theory and predict the threshold reversal fluence. The experiment to form domain reversal via direct illumination with femtosecond laser in Y-cut lithium niobate samples was conducted at room temperature. The multi-ring-like structures on the processed samples tally with the inversion window theory and the calculated threshold reversal fluence is well within the scope obtained by simulation, which serves as a corroborative evidence to prove the domain reversals can be formed by direct irradiation with femtosecond laser in lithium niobate.     

在固体透明材料中利用级联四波混频方法获得宽带多色飞秒激光脉冲的研究

飞秒激光光谱学实验研究的深入与拓展对飞秒激光脉冲的要求也越来越高.比如多色抽运探测实验需要同时用到多个不同频率的超短飞秒激光脉冲.本文设计了一个更加简单紧凑的实验装置,对两束不同中心频率的入射光引入相反啁啾,在厚度为0.5 mm的CaF2晶体中利用级联四波混频获得了光谱半高全宽近100nm,支持傅里叶转换极限脉宽小于10 fs的多色飞秒激光脉冲.这一结果将为拓展飞秒激光光谱学研究和应用发挥重要作用.     

飞秒激光烧蚀硅表面产生微纳结构过程中激光脉冲数目的影响

为了研究飞秒激光脉冲数目与硅表面形貌之间的关系,在相同的SF6气体氛围下,改变照射硅表面的飞秒激光脉冲数,发现在飞秒激光照射下由硅表面形成的微型锥状尖峰的高度与飞秒激光脉冲数呈现一种非线性关系.通过对该关系的研究有利于找出在制造具有较高吸收效率的高微型锥状尖峰的"黑硅"的实验条件,有利于基于"黑硅"材料的光电器件转化效...