Research On Raman-pulse-assisted Atom Interferometer

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.