机载激光器聚光腔的设计及试验

分析了影响固体激光器聚光腔效率的各种因素,对激光器的泵浦效率相对于聚光腔的几何形状、反射面镀层及冷却方式的关系进行了试验研究,提出了机载激光器聚光腔的设计原则。     

温度对半导体激光器退化的影响

采取等效电路模型仿真和加速退化试验相结合的方法研究温度对半导体激光器不同退化模式的影响规律。针对半导体激光器有源区退化和腔面退化进行分析,发现有源区退化会使半导体激光器阈值电流增大,而腔面退化会使半导体激光器斜率效率减小;进行了半导体激光器热特性建模与仿真,发现温度升高会使半导体激光器阈值电流增大;利用半导体激光器加速退化试验平台进行了半导体激光器加速退化试验。仿真与试验结果证明:温度升高会加剧半导体激光器腔面退化,而对有源区退化无显著影响。上述结论对进一步完善半导体激光器温度-退化仿真模型,研究温度对半导体激光器退化的作用机理和防护措施有积极作用。     

化学激光气流污染及清洁方式对腔镜反射率的影响

利用光腔衰荡光谱法对氧碘化学激光器(COIL)经气流污染及清洁后的高反射镜反射率进行了一系列的测量研究.测量结果显示,气流中的某些物质会对腔镜造成污染而使其反射率下降,采用不同的清洁方式对反射率的提高程度有很大差别,First ContactTM溶液清洁腔镜对其反射率的提高有显著作用.     

一种非稳腔调腔干涉条纹的建模与仿真

非稳腔的计算机辅助准直技术对于保证高能激光器运行参数的稳定性具有非常重要的作用.文章从理论上阐明了非稳腔调腔干涉条纹形成的物理机理,建立了正支共焦非稳腔内多光束干涉的物理模型,引入失调元件的增广矩阵来描述腔镜失调引起的椭圆高斯光束传输效应、高斯光束中心的偏移效应和附加的相位倾斜效应.使用高斯光束传输的ABCD矩阵计算了调腔光束在腔内多次往返后的高斯光束复参数,将多次往返的高斯光束进行相干叠加,获得了非稳腔不同失调角情况下的调腔干涉条纹图样,定量计算了不同失调角情况下调腔干涉条纹间距的偏移量,并与实验结果进行了对比分析.结果表明在实验误差允许的前提下,仿真得到的干涉条纹图样与实验获得的干涉条纹图样具有一致性,从而证实了理论模型的正确性.理论模型的成功建立使谐振腔的失调量与干涉条纹的形态变化精确对应起来,从而可以为非稳腔计算机辅助调节的闭环控制研究提供理论指导.     

化学氧碘激光器光腔边界层的被动控制方法实验

针对化学氧碘激光器(Chemical Oxygen-Iodine Laser, COIL)光腔内边界层的被动控制方法,设计了三种实验件。光腔的上下壁板是可拆卸的,可以更换不同的实验件,以此比较边界层的控制效果。实验结果表明:开槽板、主流引射缝和开孔板在对光腔边界层的控制上都取得了一定的效果,改善了光腔特别是光腔后半部分的压力分布。在一定范围内,增加边界层的抽气量,可以进一步减小边界层厚度,降低光腔压力,同时提高COIL出光功率,但是当抽气量过大时,反而会降低出光功率。三种实验件中,主流引射的方式对抽气量最敏感,当抽气量增加至5%时,COIL出光功率已经明显下降;开孔板对抽气量不太敏感,抽气量从1%增加至7%,对COIL出光功率的影响并不明显。     

介绍一种激光冷却液

一、概述高重复频率的晶体(YAG·红宝石或钕玻璃等)、脉冲氙灯成聚光腔若不冷却,工作温度越高,输出能量和效率越低(因温度升高,使谱线加宽,量子效率降低),所以,只有和冷却系统配合,才能正常工作。目前,国内所用冷却液主要是水,多数是用蒸馏水。有的还在水中加入少量的重铬酸钾或亚硝酸钠,也有的加入少量的高锰酸钾,以滤     

双包层光纤激光器有无损耗时的输出特性比较

从对线形腔掺镱双包层光纤激光器的输出特性进行的研究,得到了激光器泵浦阈值功率、输出光功率的表达式,并重点比较了有损耗和无损耗时光纤激光器的输出功率随光纤长度、后腔镜反射率、泵浦功率变化的关系,得出:由于损耗的存在,激光输出功率会有一定的下降,并且这个下降会随着光纤长度、后控镜反射率、泵浦功率的变大而更加显著。     

基于VCSEL实时点到点OFDM光信号在MMFs中的传输

通过实验,在使用未冷却直调3.63 GHz垂直腔面发射激光器的简单强度调制和直接检测系统中,首次证明在800 m OM2多模光纤上采用正交频分复用技术进行64 QAM(正交幅度调制)编码实现实时点到点通信,传输速度为11.25 Gb/s,功率损失1 d B。     

HF化学激光器光腔流场荧光光谱分析

化学发光方法是HF/DF化学激光器光腔流场参数的重要实验测量方法.观察并记录了在增大H2流量时,电激励HF激光光腔流场可见光荧光的变化现象,对光轴处可见光荧光进行了光谱测量.对激光器光腔内介质成分进行了理论分析,HF高阶泛频谱线计算结果显示第3振动激发态到基频的跃迁谱线处于红外区.通过对荧光实验测量光谱与光腔内介质谱线...     

DF透反仪(差动型透射率反射率测量仪)

从事激光工作的人都知道,在激光器特别是气体激光器方面,腔片的性能影响很大。经过调研,知道我国与国际先进水平差距最大恰恰在腔片上。而妨碍腔片性能迅速提高的主要因素之一是缺乏精确、可靠且较简单的测量仪器。对于我们从事的科研项目,对腔片性能的要求更是成败攸关的生命性。因此,在大力开展镀膜研究的同时,我们设计了一台对腔片、玻片及其它试样的反射率、透射率的测量仪,从75年夏天开     

前喷管燃气流对火箭飞行稳定性的影响

本文分析了具有前喷管的火箭弹在主动段的受力情况。指出,当超音速飞行时,在前喷管附近的弹体表面上产生一个局部高压区,由此形成一个翻转力矩。从而解释了在主动段超音速飞行中为什么会出现不稳定飞行。     

THE CREATION OF THE ICC

The implications for African states of the recently created International Criminal Court should be carefully considered. There are far-reaching limitations placed on the ICC's jurisdictional scheme, both temporally as well as by the preconditions to the exercise of jurisdiction in the form of territoriality and nationality. The Court's powers may also be constrained out of deference to the grant of an internationally acceptable amnesty, and national courts may be constrained to recognise immunities from prosecution for high-ranking officials. These limitations need to be properly understood so that the ICC can be effectively utilised by African States to declare and act upon their commitment to the principle of individual criminal liability for those responsible for the most serious crimes.     

THE LAND IS THE ECONOMY

This article revisits Zimbabwe's land question from the vantage point of having been written five years after the ‘fast-track’ land redistribution programme was launched. Without belittling the accomplishments of land reform in the first 19 years of the country's independence, it is generally clear that the sweeping programme of 2000–2003, the most comprehensive of its kind, created a new paradigm. Clearly, the consequences will take many years to work themselves out through the country's political, economic and social fabric.

The article briefly defines what may be termed ‘old’ and ‘new’ versions of Zimbabwe's land question before outlining the salient aspects of the reform process itself. It then assesses the outcomes of the redistribution, the apparent lacuna between ‘land’ and ‘agrarian’ reform, and the debate that the reform process itself has kindled. Transforming land distribution into qualitative agrarian reform has proved an Achilles heel in the arguments put forward by the proponents of the fast-track programme. Finally, recommendations are provided as to what is necessary to secure land and agrarian reform in the short, medium and long term.     

THE REAL STORY BEHIND THE MAKING OF THE FRENCH HYDROGEN BOMB

Based on the first-person account of coauthor Pierre Billaud, a prominent French participant, this article describes for the first time in such detail the history of the development of the French hydrogen bomb in the 1960s and the organization of military nuclear research in France. The authors illustrate the extent to which French defense and governmental authorities did not support research on thermonuclear weapons until 1966. Billaud, a project insider, relates the historical episodes that led to France's successful 1968 thermonuclear test, including the names of the individuals involved and how a timely tip from a foreign source hastened the success of the first H-bomb test.     

THE PLACE OF THE AFRICAN COMMISSION IN THE NEW AFRICAN DISPENSATION

The mandate to promote human rights in Africa is a challenging one and the African Commission on Human and Peoples' Rights, whose mandate it is, will have to use partnerships, such as NEPAD and other supportive multilateral institutions to fulfil it. The African human rights enforcement mechanism can only be as strong as the African peoples themselves make it. This paper examines the African Commission on Human and Peoples' Rights and looks at the role of the Commission in the New African dispensation following the adopting of the Constitutive Act of the African Union and the adoption of the New Partnership for African Development (NEPAD).     

ACHIEVING THE VISION OF THE NPT

This article assesses the prospects for a strategy of incrementalism to lead to achievement of the core bargain of the Treaty on the Non-Proliferation of Nuclear Weapons: non-nuclear weapon states' nuclear nonproliferation in exchange for nuclear weapon states' nuclear disarmament to the point of “global zero.” Game theory, prospect theory, and liberal international theory are used to evaluate the potential of a strategy of incrementalism. While separately each has insights to offer, it is when all three theoretical approaches are used in tandem that meaningful explanatory gains emerge. The article concludes that incrementalism probably cannot lead to complete nonproliferation and global nuclear zero. Instead, signal events (as described by prospect theory) are needed to “punctuate” incremental processes in negotiations (best explained by liberal international theory) in order to move past hindrances such as international structural constraints (exemplified by game theory) and the conservative risk-taking propensities of state elites (described by prospect theory).     

图象存储体与PC机接口设计

本文研究利用PC机扩充槽设计图象存储体与PC机的DMA接口,包括接口电路和接口驱动程序。主要完成图象存储体与PC机内存间DMA数据传送的启动及相应控制信号的产生、转换,并提供数据通道,本接口应用于“脉冲X光医疗诊断系统”,对其它图象处理系统的计算机接口亦有参考价值。