【作者】 郑丽玲；

【导师】 徐云飞；

【作者基本信息】 浙江大学 ， 光学， 2011， 硕士

【摘要】 近二十年来,激光冷却原子的研究与应用越来越受到关注,并且取得了丰硕的成果。在以往的研究中,用于冷却原子的激光均为相干光。本硕士学位论文利用部分相干光作为冷却中性原子的光源,研究了相干性对冷却原子的影响,从实验上得到了冷原子的温度随激光相干性的变化关系,并从理论上作了分析。本文的主要内容如下：第一章回顾了激光冷却原子的发展历程,概述了本文的研究的背景、研究目的和意义。并简要地描述了本文的主要工作。第二章从Rb原子的能级结构、光与原子的相互作用、磁光阱和偏振梯度冷却等出发,对激光冷却原子的基础理论进行概述。第三章首先对部分相干光的理论和特性作了简单介绍,然后介绍了部分相干光的产生机制。我们利用晶体来调制冷却激光的相位分布,从而改变了冷却激光的空间相干性。通过改变加在晶体上的外加电压,激光的相干度可以被控制。第四章对激光冷却原子所涉及的实验的各个部分进行了详细的介绍,包括激光系统中的饱和吸收、磁光阱、TOF温度测量法等。接下来介绍了实验的过程包括实验光路图的搭建。最后对所得的实验结果进行了分析。通过对比不同相干度的激光所捕获的冷原子的温度的差别,得出激光相干度对冷原子的影响。最后,总结全文,提出存在的不足之处以及需要改进的地方。更多还原

【Abstract】 In the recent twenty years, the researches on laser cooling and trapping neutral atoms and related applications attracted more and more attentions, and many fruitful results have been achieved. However, in the previous studies, the laser beams used to cool atoms are usually coherent. In this thesis, the cooling and trapping neutral atoms by partially coherent laser beams is investigated. The influences of coherence degree of laser beam on the temperature of cold atoms in the MOT is obtained experimentally. The results are analyzed theoretically. The main contents of the thesis are as follows:In the first chapter, an introduction to the historical background and developments of laser cooling is presented. Then the research background and the purpose of this study are introduced briefly.In the second chapter, the atomic energy level structure of rubidium atom is discussed. The basic principle of the interaction force between atom and laser, the laser cooling and trapping in magneto-optical trap are introduced briefly.In chapter 3, the theory and method to obtain partially coherent light is introduced. We use the crystal to modulate the phase distribution of the laser. By changing the voltage applied on the crystal, the degree of coherence of laser beam can be controlled.In chapter 4, the experimental setup of laser cooling is described. Each parts of the experimental setup are introduced in detail, including the main structures and the operating principles of the semiconductor diode laser system, frequency stabilization, magnetic system, and time-of-flight measurement method of the temperature of cold atoms. Then the experimental procedure and results of cooling atom by partially coherent laser in the magneto-optical trap are presented. By analyzing the results, we find out that with the decrease of the coherence degree of the laser beam, the temperature of cold atoms in the MOT increases.In chapter 5, a brief conclusion is presented. The main results of the thesis are summarized and an outlook is given.更多还原