微型自由电子激光器的Maxwell方程解

本文由Maxwell方程导出了微型自由电子激光的电子辐射能量方程,上述微型自由电子激光器是利用铁电单晶体强大周期性表面势来设计的。 微型廉价自由电子激光器有高增益。     

世界首台反激光器研制成功

1960年7月第一台激光器问世。激光器是指将窄幅频率的光辐射线,通过受激辐射放大和必要的反馈共振,产生准直、单色、相干光束的仪器。目前激光器使用的增益媒介大多是砷化镓半导体,用以产生一束聚焦的相干光束,这种光束有相同的频率和振幅,且运行方向一致。与激光器发射激光不同,     

摆动场中的电子动力学与系统的稳定性

从自由电子激光器的摆方程出发,利用Jacobian椭圆函数和椭圆积分分析了系统的相平面特征,并利用加速器概念和束流动力学方法,讨论了系统的稳定性、增益和临界特征等问题.结果表明,由于外力矩存在,自由电子与辐射场的同步性质得到了改善,而系统的能量转换率也得到了提高.但是,由于稳定区面积减小,系统的稳定性和辐射强度受到一定影响.如何综合考虑这两种因数是自由电子激光器设计的重要环节之一.     

自由电子激光器的新进展

本文对自由电子激光器的工作原理、实验装置以及自由电子激光辐射的基本特征等进行了详细介绍，在系统综述自由电子激光器的发展动态的基础上，指出了这一研究领域的发展趋势。     

太赫兹自由电子激光器研究进展

自由电子激光器是目前可以获得太赫兹最高输出功率的辐射源,是一种较为理想的太赫兹源。本文主要论述了太赫兹自由电子激光的发展历史和现状,并对其发展趋势作了一定的分析和综述。太赫兹自由电子激光器技术的发展必将大大推进太赫兹成像、检测技术的发展．对相关领域科学研究、国家安全等方面有着重大影响。     

钙蒸气中的紫外相干辐射特性研究

用氮分子激光器泵浦的两台染料激光器(输出光频率分别为ω_1和ω_2)二步激发钙蒸气,由不等频二步共振和不等频双光子共振四波混频ω_1+ω_2-ω_(IR)=ω_(UV)(ω_(IR)为红外受激辐射频率),产生了波长为272.2nm的紫外相干辐射,并对其激发和辐射特性进行了研究.     

利用相干渡越辐射测量自由电子激光的群聚

探讨了利用相干渡越辐射(CTR)来测量自由电子激光(FEL)群聚电子束的测量方法。根据相干渡越辐射(CTR)的特性,结合FEL中电子束群聚的特点,建立了理论模型。利用CAEP光阴极RF腔注入器、30 M eV射频加速器产生的30 M eV电子束及相应的FEL装置进行了实验验证。结果表明:群聚后电子束渡越辐射的强度大大高于非群聚电子束的辐射强度,而且辐射角也很小,反映了该辐射的相干性,由此可以给出电子束的群聚效果。     

自由电子激光的初级理论探讨

本文分析了一种典型的自由电子激光器———圆极化静磁Wiggler自由电子激光器的线性理论 ,得到了电子满足的非线性方程 分析表明 ,电子能量的一阶扰动平均值对激光的建立没有贡献 ,贡献来自二阶扰动 最后给出了小信号增益     

基于微型谐振腔的史密斯-帕赛尔自由电子激光

研究了一种由电子枪、微谐振腔、金属光栅和集电极组成的新型史密斯-帕赛尔自由电子激光.利用PIC三维模拟,讨论了该装置的特点.发现在合理的电子能量和光栅参数下,该装置可以产生THz频率范围内的相干高功率脉冲SPR.研究结果表明,当电子束能量E=50keV,电子束电流I=10A时,光栅周期L=0.3mm时,可以得到功率在4 000W左右、脉冲为0.25ns的514.643GHz的太赫兹辐射.     

3-5μm中红外光源产生概述

讨论了各类中红外激光器,如气体激光器、化学激光器、自由电子激光器、半导体激光器、固体激光器和光参量振荡激光器,尤其重点分析了基于非线性光学理论的中红外光学参量振荡激光器。通过比较各种中红外激光器的优缺点,可以得出中红外光参量振荡激光器将是未来产生3-5μm中红外光源的最重要的方法之一。     

Hard X-ray free-electron laser based on echo-enabled staged harmonic generation scheme

A novel approach to producing coherent hard X-ray based on the echo-enabled staged harmonic generation (EESHG) free-electron laser scheme is proposed. This scheme is not a simple cascaded echo-enabled harmonic generation (EEHG) but consists of an EEHG and a conventional high-gain harmonic generation (HGHG) like configuration, which also works in the EEHG principle. It is shown that fully coherent hard X-ray radiation can be obtained directly from a conventional VUV seed laser with reduced size and cost in c...     

CAEP-FEL装置自发辐射和同步辐射分析

在自由电子激光振荡器中，电子在摇摆器产生的自发辐射与在偏转轨道上产生的同步辐射同时存在，自发辐射是与受激辐射密切相关的过程。分析对比了同步辐射与自发辐射的强度和频谱分布，并与实验结果进行了比较。     

K模辅射场与二能级原子作用系统中原子的偶极压缩

利用J-C模型,在旋波近似下,给出了K模相干光场与二能级原子相互作用系统中系统态矢的演化。利用数值计算方法研究了三模相干光场与二能级原子相互作用系统中原子的偶极压缩效应,讨论了初始光场强度和光场相位对原子的偶极压缩效应的影响。结果表明:当初始光场较强时,原子只在演化的初期呈现短暂的间隙性压缩效应,光场相位决定原子的压缩方向,而光场强度变化对原子的偶极压缩效应影响很小。     

电磁场辐照下量子线的两能级电子波函数

从理论上研究了在横向极化的外电磁场辐照下量子线的电子态．使用量子光学中两能级原子与电磁场相互作用的半经典方法,得到了在自由电子和弱场假设下两能级电子与场相互作用的波函数表达式．此波函数包含了外场的频率和强度以及量子线的几何参量,由此可研究决定系统与时间有关的输运性质．     

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.     

自由电子激光与混沌

对自由电子激光的混沌问題作了评述,讨论了自由电子激光中电子与光场的不稳定性、电子轨道混沌与光场混沌之间的相互影响与关联。指出用混沌理论研究手段对探索自由电子激光的重要意义和途径。     

Electron Beam Spectrum Diagnostics with Optical Transition Radiation on the Beijing Free-Electron Laser

A measurement system was developed to measure the electron beam spectrum of the Beijing free-electron laser based on the optical transition radiation (OTR). This paper describes the system, which consists of a 32-channel high resolution of 0.02% OTR detector, especially the spectrometer. The OTR an- gular-distribution pattern at the focal plane has two apexes, but the two apexes are smoothed out due to theel ectron beam energy distribution. The energy spectrum can be measured if the magnet energy resolution is higher than 0.7% to distinguish the electron beam energy distribution.     

部分相干环形涡旋的特性研究

根据部分相干光的传输理论,介绍了部分相干涡旋在光源平面上光强的分布情况,并以环形涡旋光束为例,做了详细的分析,得出相对宽度s/w0和拓扑荷数m的变化,对z=0截面上的光强I分布的影响。还给出了两束平行、离轴的部分相干环形涡旋光束叠加合成的相干涡旋,分析了在叠加场中光强I随离轴相对距离d/w0和相干参数α变化的情况,并且在相干极限α→∞时,复合相干光涡旋就转化成复合光涡旋。     

Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight

The morphology of micrometre-size particulate matter is of critical importance in fields ranging from toxicology to climate science, yet these properties are surprisingly difficult to measure in the particles' native environment. Electron microscopy requires collection of particles on a substrate; visible light scattering provides insufficient resolution; and X-ray synchrotron studies have been limited to ensembles of particles. Here we demonstrate an in situ method for imaging individual sub-micrometre particles to nanometre resolution in their native environment, using intense, coherent X-ray pulses from the Linac Coherent Light Source free-electron laser. We introduced individual aerosol particles into the pulsed X-ray beam, which is sufficiently intense that diffraction from individual particles can be measured for morphological analysis. At the same time, ion fragments ejected from the beam were analysed using mass spectrometry, to determine the composition of single aerosol particles. Our results show the extent of internal dilation symmetry of individual soot particles subject to non-equilibrium aggregation, and the surprisingly large variability in their fractal dimensions. More broadly, our methods can be extended to resolve both static and dynamic morphology of general ensembles of disordered particles. Such general morphology has implications in topics such as solvent accessibilities in proteins, vibrational energy transfer by the hydrodynamic interaction of amino acids, and large-scale production of nanoscale structures by flame synthesis.     

Raman型原子激光制备过程中光场的压缩特性

研究了Raman型原子激光制备过程中探测光场的压缩特性．这种原子激光是利用钠原子玻色-爱因斯坦凝聚体（BEC）与一束较弱的压缩相干态探测光和一束较强的经典泵浦光Raman跃迁相互作用制备得到的研究结果表明,压缩相干态探测光在原子激光制备过程中呈现周期性压缩,其压缩周期与原子阱中的平均原子数、光场与原子BEC相互作用强度及光场的失谐量等因素有关,压缩深度决定于探测光场的初始压缩因子．