【作者】 韩顺利；

【导师】 林强； 王兆英； 徐云飞；

【作者基本信息】 浙江大学 ， 光学， 2010， 博士

【摘要】 近二十几年来激光冷却原子的研究取得了丰硕的成果。低速超冷的中性原子为物理学家研究物质波开启了一扇新的大门,超冷原子的研究与应用越来越受到关注,并由此产生了一门新兴的学科—原子光学。在原子光学的众多应用中,原子干涉仪特别引人注目。利用对拉曼激光脉冲在时间和空间上的精确控制,从而使超冷原子波包相干地完成分束、合束、再分束的过程,这样不同的原子波包就会历经不同的演化路径获得不同的位相,最终形成干涉条纹,从而得到类似于光学干涉仪的原子干涉仪。通过对原子干涉条纹位相的精密测量,就可以反演出物质波包在传输过程中由于路径不同而携带的外场信息。第一章简要介绍了原子光学的历史背景、发展历程以及潜在应用,描述了冷原子干涉仪的发展现状以及应用前景。阐述了我们开展冷原子干涉仪研究的必要性,并简要地描述了本文的工作重点。第二章首先从原子的能级结构、塞曼效应、斯塔克效应、激光与原子的相互作用力、磁光阱(包括二维磁光阱和三维磁光阱)等出发,介绍了激光冷却与陷俘的基本原理；然后详细地描述了受激拉曼跃迁以及拉曼脉冲型原子干涉仪的基本理论,其中对干涉仪的相位移动做了仔细分析。第三章对冷原子干涉仪实验所涉及的各个部分进行了详细的介绍,其中包括真空系统、磁场系统、半导体激光器系统、移频稳频稳相系统及微秒量级的程序控制系统的工作原理和主要构造。重点分析了现有的光栅反馈外腔式半导体激光器的功率放大、移频、稳频和稳相技术的优缺点,并在此基础上做了相应改进,提出了注入锁定和新的激光器移频、稳频和稳相等实验技术。第四章主要介绍了我们原子干涉仪实验的研究进展。首先搭建并测量了二维磁光阱,其高粒子流输出完全可以满足干涉仪所需要的三维磁光阱的装载率。经过偏振梯度冷却、原子能态制备和拉曼光的制备,结合原子能态探测技术,拉曼光与原子相互作用的拉曼谱、拉比振荡、干涉条纹等都已经在实验室中实现。第五章是对全文主要结果的总结和对未来研究的展望。更多还原

【Abstract】 Laser cooling and trapping has obtained very fruitful results in recent twenty years. Low-speed,namely ultra-cold, neutral atoms open a new door to investigate the characteristics of matter waves for the physicist. The research and applications of ultra-cold atoms attract more and more attentions, and thus form a new subject-atom optics.Among many applications in atom optics, we will focus on atom interferometer. By using the precise control of the Raman laser pulses in time and space, the coherent ultra-cold atom wave packet is splitted, combined, and then re-splitted in the process. Then the atomic wave packet will acquire different phase because of the different evolution path. At last, the interference fringes, which are similar to the optical interferometer, are seen in atom interferometer. Meanwhile, the matter wave packets in the different evolution path will bring the information of the outside field, so the field information can be deduced through the precision measurement of atomic interference fringes phase.In the first chapter, an introduction to the historical background, developments and potential applications of atom optics is presented. Then the advantages, development status and application prospects of cold atom interferometer in the field of atom optics are described. The necessity of carrying out the atomic interferometer experiments is stressed. Meanwhile, a brief description about the focus of this thesis is introduced.In chapter 2, the theory of Raman-pulse-assisted atom interferometer is introduced. We first discuss the conceptions of the atomic energy level structure, Zeeman effect, Stark effect,the interaction force of atom and lasers, Magneto-optical Trap (MOT, including the two-dimensional and three-dimensional MOT), etc. Subsequently, the basic principle of laser cooling and trapping is briefly introduced. In addition, we provide a detailed and thorough descriptions of stimulated Raman transition and the theory of the Raman light-pulse atom interferometer,especially the analysis of the phase shift.In chapter 3, the experimental setup of Raman-pulse-assisted atom interferometer is described. Each parts of the experimental setup are introduced in detail, including the main structures and the operating principles of the vacuum system, magnetic system, semiconductor diode laser system, frequency shift, frequency stabilization, phase stabilization system and the computer controlling program in microsecond precision. Based on the existing techniques of power amplifier, frequency shift, frequency stabilization and phase stabilization, the corresponding shortcomings are improved. In addition, the new experimental schemes of injection-locking, frequency shift, frequency stabilization and phase stabilization were proposed and constructed.In chapter 4, the experimental procedure and results of Raman-pulse-assisted atom interferometer were presented. The preliminary results and descripitions of the experimental procedure in our atom interferometer laboratory are contained in this chapter. A two-dimensional magneto-optical trap (2D MOT) with push beam has been assembled and detected, which delivers a sufficiently atom flux for the desired loading rate of the three-dimensional magneto-optical trap (3D MOT). After polarization gradient cooling, state selection and Raman laser preparation, Raman spectrum, Rabi oscillation and interference fringes are observed through the interactions of 87Rb atoms and Raman lasers.In chapter 5, a brief conclusion is presented. The main results of the thesis are summarized and an outlook is given about the future of Raman-pulse-assisted atom interferometer.更多还原