光纤激光器相干合成理论分析及模拟仿真

基于光纤激光器相干合成实验的需要,给出了基于双高斯光束理论的光纤激光器模型方程,并推导出了双高斯光束在空间位置的干涉模型。在此基础上,模拟仿真了空间距离,光束夹角,偏振特性,振幅之比,频率等因素对双高斯光束相干合成的强度分布影响,分析讨论双高斯光束的参数对相干合成效果的影响。     

高折射率和不透明粒子的拉曼光谱和光学捕陷

用倒置的共焦—激光镊—拉曼谱仪系统，测量了悬浮在液体中的单光学捕陷的高折射率和非透明微粒子的拉曼光谱。用低功率TEM00模的二极管激光束，既做光学捕陷，又做具有折射、吸收和反射的金属微粒的托曼激发。为对不透明微粒形成稳定的捕陷．把光束聚焦在近粒子的顶部．并通过轴向推斥力将粒子推向背面的玻璃板。记录了具有高折射率的微米尺寸单品，如硅、锗和KNbO2的拉曼光谱．以及黑色和彩色涂料吸收粒子的拉曼光谱，还展示了捕陷银粒子簇表面吸收的若丹明6G和苯基丙氨酸分子表面增强拉曼散射。     

一种新型的钠原子磁光陷阶（MOT）

一种新型的钠原子磁光陷阶（ＭＯＴ）磁光陷阱是冷却和捕获超冷原子的主要方法，目前国际上不少实验室中均已获得超冷原子气体。磁光陷阱的工作原理是在超高真空（１０７Ｐａ）钠原子吸收池中，用六束激光（上、下、左、右、前、后）交汇于吸收池中心。同时在吸收池上装有...     

原子磁导引

８０年代中期以来,激光冷却和捕陷中性原子技术的长足进步,使得制备极低温度的原子气体成为可能,一门新兴的学科分支一冷原子物理学迅速崛起．一般将温度Ｔ＜１ｍＫ的原子称为冷原子（ｃｏｌｄ　ａｔｏｍ）;将Ｔ＜１～１０ｕＫ的原子称为超冷原于（ｕｌｔｒａｃｏｌｄ　ａｔｏｍ）．在这样低的温度下,原子的质心运动速度已很低,对应的ｄｅ　Ｂｒｏｇｌｉｅ波长（　ｄｅ）已很长,因此原子体系具有很多新的物理性质,出现许多新的物理现象．例如,原子光学（一个原于物理和光物理交叉的新领域,在这个领域中,人们类似光物理中处理光（…     

强聚焦激光束俘获生物粒子

激光束与透明生物粒子的相互作用中,激光束的力学效应明显地超过热学效应和光生物化学效应。适当的光束配置可以造成一个能捕捉和操纵生物粒子的激光陷阱。本文介绍一种强聚焦氦氖激光束的纯光学陷阱,以及用它阱陷红葡萄球菌、球形鞭毛虫等生物粒子的实验。四十毫瓦功率的激光束     

软X射线辐照引入于SiO_2中的中性陷阱

本文用雪崩热电子注入技术与MOS C-V技术,研究了软X射线辐照引入于SiO_2中的中性陷阱的性质.给出陷阱俘获截面σ为10~(-15)～10~(-16)cm~2,有效陷阱密度为10~(11)～10~(12)cm~(-2).发现陷阱密度随辐照时间的增加而升高,但很快趋于饱和;陷阱密度并随辐照强度的提高而增大.文中研究了室温及77°K下中性陷阱的俘获特性以及陷阱的解陷作用.还给出了陷阱的退火实验结果.     

激光冷却和捕陷气体原子或分子

本文综述了激光冷却和捕陷气体原子和分子的新技术.这项技术是激光应用的一个新的重要发展方向.它将为光谱学、原子频标和原子物理学的研究工作提供一个有效工具.估计会在其他研究领域也将有广泛应用.     

新型径向偏振脉冲激光器

径向偏振光的在电子加速、原子陷阱和捕获、生物光镊、高分辨率显微镜技术以及高效率金属切割等领域有着非常重要的应用[1],因此通过激光器的输出来直接产生该种光束已经成为国际研究热点.但在以前的研究结果中,存在激光效率低、径向偏振纯度低以及光束轴对称性差等缺陷.     

超高斯光束经椭圆环光阑的衍射和光束质量评价

本文采用数值计算方法讨论了超高斯光束经椭圆环的的衍射现象。以桶中功率（PIB）、β参数和η参数为远场激光光束质量的评价参数,对超高斯光束经椭圆环光阑后的光束质量作了详细的研究,大量数值计算和物理分析表明,在椭圆环外径一定的条件下,超高斯光束经椭圆环衍射后的光束质量与椭圆环的遮拦比和超高斯光束的阶数有关。     

指数响应的强非局域介质中正交偏振双厄米高斯光束传输特性

运用变分法研究了具有e指数响应的强非局域介质中两束正交偏振、中心重合的厄米高斯光束的传输特性,得到了光束各参量的演化方程和一个临界功率Pc。当两光束以临界功率入射时,可以形成厄米高斯型空间光孤子;当两光束以总功率2Pc入射,但两光束入射功率不相等时,两光束可以形成厄米高斯型呼吸子。通过数值模拟研究发现,低阶光束时,可以得到近似孤子解;当光束阶数大于3阶时,则得不到孤子解。比较变分解与数值解,结果表明在光束阶数小于3阶时,变分解较好的反映了具有e指数响应的强非局域介质中两束正交偏振、中心重合的厄米高斯光束的传输特性。     

Hole trapping in E-beam irradiated SiO2 films

Low energy (25 kV) electron beam irradiation of MOS capacitors is shown to produce neutral hole traps in thin ‘radiation hardened’ SiO₂ films. These traps are found in an uncharged state after irradiation and are populated by passing a small hole current, generated by avalanche breakdown of then-type silicon substrate, through the oxide. From the time dependence of the observed trapping, a capture cross-section between 1 × 10∼⁻¹³ and 1 × 10⁻¹⁴ cm² is deduced. The trap density is found to depend on the annealing conditions and incident electron beam dosage. The density of traps increases with incident electron beam exposure. Once introduced into the oxide by the radiation the traps can be removed by thermal anneals at temperatures above 500° C. Parallels between electron and hole trapping on these neutral centers are strong evidence for an amphoteric uncharged trap generated by ionizing radiation.     

A hybrid laser-magnet trap for spin-polarized atoms

This paper presents a brief survey of theoretical issues related to a hybrid laser-magnet trap for neutral spin-polarized atoms. At low densities, such a trap might be used to address a number of fundamental questions, e.g. the interaction of an individual atom with an electromagnetic field, while at high densities it might be used for “containerless” preparation of bulk amounts of a new metastable form of matter, spin-polarized atoms. In particular, a discussion is presented of the feasibility and limitations of a trap based on a near-resonant CW TEM^*₀₁ (“doughnut mode”) laser beam, which provides trapping in two dimensions, and on a strong homogeneous solenoidal magnetic field (the axis of which is also the laser axis), which provides trapping in the third dimension.     

空心新型光阱的实验研究

介绍了用锥镜法和取高级衍射光斑法来实现空心光阱的实验方法。用实验定性地证明了空心光阱轴向捕获力高于实心光阱。用图像分析法比较了空心光阱与实心光阱近中心横向光阱刚度 (光焦点附近小范围内的光阱横向刚性程度 ) ,表明同等条件下空心光阱的近中心横向光阱刚度弱于实心光阱。用流体力学法测量光阱的逃逸阱力随光功率的变化 ,表明同等条件下空心光阱的逃逸阱力大于实心光阱 ,因此空心光阱操纵微粒具有更高的稳定性。同时指出了空心光阱具有更低的热损伤 ,在低倍物镜下空心光阱具有更高的实用价值 ,以及空心光阱适于更加高精度的实验操作     

环形光对光阱有效捕获力的提高

定义了光阱的有效捕获力 ,然后在几何光学范围内计算了环形光束形成的光阱———空心光阱的有效捕获力 ,并把空心光阱与实心光阱产生的光阱有效捕获力作了比较。数值计算结果得到空心光阱的有效捕获力大大提高 ,光阱的稳定性也随之提高 ;而且空心光阱对捕获对象的热损伤效应相应减小。     

Good and bad aspects of traps for neutral particles

We exhibit a configuration of magnetic fiedls which has a field minimum at its center and is therefore suitable for trapping paramagnetic neutral atoms or molecules. The trap has a large field component along the axis and is therefore conducive to high resolution spectroscopy. We propose an RF-laser cooling cycle which appears to be capable of attaining ultimate temperatures of 10^-6K. Limits to the attainable resolution due to this temperature are discussed.

In order to label the properties of traps for neutral particles as “good” or “bad” it is necessary to have some value system. Mine is that good properties enhance the utility of these traps for studies of properties of the trapped atoms: precise spectroscopy of their levels, collision studies using a dense cold target, and possibly the “solid state” physics of their mutual interaction at high density. (From the contrasting perspective of interesting and/or challenging physics relating to slow atoms, the labels good and bad may well be reversed!)     

基于激光冷却技术的中性锶原子特性研究

为了研究碱土金属类的中性锶原子在多普勒冷却激光场中的冷却特性,从Heisenberg方程出发,采用激光冷却理论分析得到锶原子在能级跃迁（5s2）1S₀~（5s5p）1P₁ 1维驻波激光光场和3维磁光阱中冷却效果与激光强度、失谐量等冷却激光场参量的关系。结果表明,当锶原子处在1维驻波激光光场中且在弱激光光场、频率小失谐条件下,锶原子所受耗散力与这两个参量呈线性关系,但当两个参量增长至一定程度时耗散力呈现饱和现象;当锶原子在3维磁光阱中且当阱中激光光场的频率失谐为-16MHz时,碱土金属锶原子有最低冷却温度,约为0.76mK。对多普勒冷却光场中性锶原子特性的分析为其它碱土金属类原子的冷却研究提供了一定的理论指导。     

Study of deep level in bulk P-InP by admittance spectroscopy

We report the application of diode admittance spectroscopy in characterising traps in Mg-doped InP. Measurements performed on Au-InP Schottky diodes have identified a hole trap located 0.15 eV above the valence band of InP. Other characteristic parameters such as trap density and hole capture cross-section have also been determined, with results suggesting hole capture at a neutral trapping centre.     

Hole trapping and trap generation in the gate silicon dioxide

Oxide breakdown has been proposed to be a limiting factor for future generation CMOS. The breakdown is caused by defect generation in the oxide. Although electron trap generation has received much attention, there is little information available on the hole trap generation. The relatively high potential barrier for holes at the oxide/Si interface makes it difficult to achieve a high level of hole injection. Most previous work was limited to an injection level Q_inj of 10¹⁴ cm^-2. In this paper, we investigate the hole trapping and trap generation when Q_inj reaches the order of 10¹⁸ cm^-2. When Q_inj <10¹⁵ cm^-2, the trapping is dominated by the as-grown traps. As Q_inj increases further, however, it is found that the generation of new traps controls the trapping. The trap generation does not saturate up to the oxide breakdown. The trapping kinetics for both the as-grown and the generated traps is studied. The relationship between the density of generated traps and the Q_inj is explored. Attention is paid to how the trapping and trap generation depends on the distance from the interface. In contrast to the uniform generation of electron traps across the oxide, we found that the hole trap generation was not uniform and it moved away from the interface as Q_inj increased     

Influence of holes on neutral trap generation

Using a newly proposed method for estimating the neutral trap density, generation characteristics of the neutral trap during various stress types have been investigated. From the analysis of the trap-generation kinetics, two types of trap generation closely related to holes have been identified. At the first stage of stress application, holes interact with the pre-existing structural origins of the neutral traps, then the neutral traps are generated. Influence of hole energy on this type of trap generation is also identified. After that, as holes pass, they also create the structural origins of the traps. The holes interact with these structural origins and the neutral traps are generated as a secondary effect. Thus, the increase in the neutral trap density shows up clearly with increase in the hole fluence. The stress-strength dependence of the increase in the neutral trap density can also be interpreted in terms of the influence of hole energy on the trap generation