平衡自场对有线性摆动器的自由电子激光器的自发辐射和受激辐射的影响

本文计算了在平衡自场、线性摆动器场和轴向磁场作用下的电子轨道,并由此求得有线性摆动器的自由电子激光器的自发辐射和受激辐射。结果表明自场有增强辐射的作用。     

在环型自由电子激光器中电子运动的混沌特性

本文分析了相对论性电子在环型摆动器磁场,轴向磁场和由非中性电子束产生的平衡自电场和自磁场中的运动。通过数值计算画出Poincare截面映射图,表明当自场足够强时,这种运动变成混沌的。虽然现实的环型摆动器场和自场一样使电子运动方程成为不可积的,但自场使运动产生混沌的作用要比摆动器场强。轴向磁场有抑制混沌发生的作用。     

Chaotic electron trajectories in a circular free electron laser

The motion of a relativistic electron is analyzed in the field configuration consisting of a circular wiggler magnetic field, an axial magnetic field, and the equilibrium self-electric and self-magnetic fields produced by the non-neutral electron ring. By generating Poincare surface-of-section maps, it is shown that when the equilibrium self-fields is strong enough, the electron motions become chaotic. Although the realistic circular wiggler magnetic field destroys the integrability of the electron motion as the equilibrium self-fields do, the role the latter plays to make the motions become chaotic is stronger than the former. In addition, the axial magnetic field can restrain the occurrence of the chaoticity.     

CHAOTIC ELECTRON TRAJECTORIES IN A CIRCULAR FREE ELECTRON LASER

The motion of a relativistic electron is analyzed in the field configuration consisting of a circular wiggler magnetic field, an axial magnetic field, and the equilibrium self-electric and self-magnetic fields produced by the non-neutral electron ring. By generating Poincare surface-of-section maps, it is shown that when the equilibrium self-fields is strong enough, the electron motions become chaotic. Although the realistic circular wiggler magnetic field destroys the inte-grability of the electron motion as the equilibrium self-fields do, the role the latter plays to make the motions become chaotic is stronger than the former does. In addition, the axial magnetic field can restrain the occurrence of the chaoticity.     

Light emission from semiconductor triode

Light emission in a novel HEMT-like structure was observed under conditions of strong reverse bias on the Schottky gate with a positive bias on the drain. Two distinct regions of light emission are present in the device with emission of red shaded light at the drain side of the gate and off-white color emission at the drain. These two distinct colors are clearly visible with the use of a microscope. The bias levels under which light emission occurs approach those necessary for catastrophic device breakdown. In the continuation of the study, spectroscopy of the emitted light is planned.     

脉冲激光外延生长YBa2Cu3O7–δ涂层导体LaMnO3缓冲层

采用脉冲激光沉积技术在双轴织构的Ni95W5(Ni-5W)合金基底上外延生长了LaMnO3(LMO)薄膜作为涂层导体缓冲层,研究了沉积温度对LMO薄膜生长织构和表面形貌的影响。研究结果表明：沉积温度对LMO薄膜的表面形貌有一定的影响;在沉积温度为650 ℃时,LMO薄膜具有良好的(00l)取向,薄膜表面平整均匀,光滑致密,其均方根粗糙度在2 nm以下;而且,在此LMO缓冲层上外延生长的YBa2Cu3O7–δ超导层具有良好的双轴织构,超导转变温度Tc为92 K,转变宽度小于1 K,临界电流密度Jc为5.3×105 A/cm2(77 K,自场)。     

Amplification of spontaneous emission in erbium-doped single-modefibers

Amplification of spontaneous emission (ASE) in erbium-doped single-mode fiber amplifiers operating at λ=1.53 μm is studied theoretically and experimentally. The ASE noise spectra obtained from the theory are found to be in excellent quantitative agreement with the experimental data. The observed changes in ASE spectral shapes under different population inversion conditions are also explained. The model may be used to evaluate the performance of erbium-doped fiber lasers as well as to assess the noise characteristics of erbium-doped fiber amplifiers as applied to wavelength-division multiplexing optical communications     

掺Yb3+光纤放大器的自发辐射噪声分析

为了研究掺Yb3+光纤放大器中自发辐射噪声分布情况,利用离散化的方法求解掺Yb3+)光纤放大器的速率方程,理论研究了不同的抽运方式、端面反射率、抽运功率以及有无滤波等条件下,端面抽运掺Yb3+光纤放大器中自发辐射的功率放大特性.结果表明,不同边界条件下的自发辐射功率差异较大;通过减少光纤端面的菲涅耳反射和利用滤波技术等方法,可有效抑制光纤激光放大器中自发辐射噪声的功率放大.     

Induced γ-ray emission

The extension of optical maser techniques to the γ-ray region is considered. It is shown that under certain conditions induced γ rays can be produced. The condition of criticality rather than that of oscillation is used because a γ-ray maser does not have a resonant structure. The main observable effects are the shortening of lifetimes of some γ excitations and the appearance of two or more coherent γ quanta. It appears to be difficult to prepare samples that will become critical. The principles are applied to a specific example.     

Studies of the emission from indium antimonide

Experimental studies on the radio-frequency emission-- from InSb under the influence of electric and magnetic fields in the range of 10 MHz to 10 GHz, including the effect of temperature variations around 77° K, are presented. Indications of very weak emission for a narrow range of electric fields in the absence of a magnetic field are observed.     

靶形与离子发射

本文报道线状聚焦激光打靶,激光等离子体发射的离子性质的实验结果。     

IGFET hot electron emission model

A new model for hot electron emission into the oxide layer of IGFETs is presented. When IGFETs operate under high gate and drain bias conditions, electrons are accelerated by the high drain field and injected into the oxide layer at a certain probability. The present model takes into account the following: (1) the energy dependence of hot electron scattering probability, (2) the three-dimensional angle at which electrons are injected into the oxide layer, (3) the quantum effect at the SiSiO₂ interface that gives the reflection probability, and (4) the scattering and reaching probabilities without energy loss. The total emission current is obtained by a five-fold integral over the energy, position and solid angle elements. The current thus predicted is expected to be two or three orders of magnitude smaller than that from Phillips' model previously proposed for IGFET emission current and hence closer to experimintal data. The present model can give the position dependence of emitted current and is suitable for incorporation into two-dimensional numerical analysis.     

Noise in space charge limited field emission devices

The noise suppression in space charge limited field emitter cathodes is calculated, and it is shown that the noise can be more strongly space charge suppressed than in thermionic cathodes. The velocity fluctuation noise of the field emitter cathode is also calculated under arbitrary space charge conditions. The results are used to evaluate the noise figure of traveling wave tubes. Low noise figures are possible if the noise suppression of the space charge limited field emitter remains intact at microwave frequencies.     

利用高斯函数拟合荧光光谱诊断龈下结石的研究

以405nm发光二极管(LED)为激发光源,分别测量了正常牙齿和牙结石的荧光光谱,由于其荧光光谱均有较宽的荧光带,且相邻的荧光峰互相重叠,不易于分析比较。用高斯函数对其进行进一步分析对比,提出了6种诊断龈下结石的评价方法,并对6种方法的灵敏度进行了分析。研究结果表明,利用波长为676和486nm处的荧光强度之比诊断牙结石具有较高的灵敏度,这一比值可以作为诊断牙结石的检测标准。     

Spatially resolved observation of visible-light emission from Si MOSFET's

Light emission from Si MOSFET's operating in the saturation region is observed. This observation provides direct evidence for the phenomenon of photocarrier generation in the substrate of VLSI's. The light emission appears to be uniform along the device width and emanates from the drain end of the MOSFET under normal operation. Light spots of much higher intensity are observed when the device is biased into the snap-back regime. This provides insights into the mechanism of snap-back breakdown.     

Spontaneous and stimulated emission from CdxHg1−x Te semiconductor films

The experimental data on observation of spontaneous and stimulated emission from thin epitaxial Cd_xHg_1?x Te films optically pumped by Nd: YAG laser radiation are reported. A simple theoretical model is suggested to describe the initiation of population inversion under these conditions. The parameters realized under the experimental conditions are theoretically estimated.     

X射线辐照下材料电子发射特性的模拟

稳态 X 射线管是一种重要的 X 射线辐照模拟装置,在辐照效应等研究领域有重要应用。采用蒙特卡罗模拟方法计算了 50 kV,150 kV 和 225 kV 管电压下的 X 射线能谱,并对 X 射线辐照下电子发射进行了模拟;研究了准直孔直径分别为 2 mm,4 mm 和 6 mm 条件下 X 射线的焦斑分布和电子发射弥散情况,以及不同能谱的 X 射线轰击到聚乙烯、聚酰亚胺、Si、SiO₂、Cu、Ta 和 W等样品上产生的电子发射能谱和电流强度等特性,为 X 射线辐照下材料电子发射特性的实验研究和设计提供一定的理论基础和指导。     

应用于白光显示的碲酸盐玻璃上转换发光特性

用高温熔融法制备了Tm3+/Er3+/Yb3+共掺碲酸盐玻璃(TeO2-ZnO-La2O3)样品,测试了玻璃样品的吸收光谱和上转换发光光谱,分析了上转换发光机理。结果发现:在975 nm,波长激光二极管(LD)激励下,制备的碲酸盐玻璃样品可以观察到强烈的红光(662 nm)、绿光(525、546 nm)和蓝光(475 nm)三基色上转换发光,分别对应于Er3+的4F9/2→4I15/2,2H11/2→4I15/2、4S3/2→4I15/2和Tm3+的1G4→3H6能级跃迁;随着Yb3+掺杂含量和泵浦功率的增加,样品的上转换发光强度都得到了一定程度的提高;通过调整稀土掺杂的浓度,得到了接近于标准白光(EE)发射。     

微腔中量子点光子发射的动力学研究

基于量子回归理论建立了微腔-量子点耦合模型的主方程,研究了用激光脉冲激发时微腔中的量子点二能级系统的密度矩阵随时间的演化,然后通过密度矩阵得出发射光子数和二阶相关度等特性,并对适合于制作单光子源的微腔参数和泵浦条件进行了优化。相关参数中,微腔衰退率和系统耦合系数的相对关系对单光子发射过程起关键作用。     

热累积效应对碳纳米管场发射特性的影响

为进一步提高碳纳米管阴极的场发射能力,分析了不同条件下碳纳米管的场发射测试结果,研究了热累积效应对碳纳米管场发射性能的影响。实验结果表明,通过抑制场发射测试过程中阳极的热累积,可获得更大的发射电流和发射电流密度。该研究为进一步提高碳纳米管阴极场发射能力提供了参考。