Cooling Of Three-level Atom In An Optical Cavity

Laser cooling and trapping are the most rapid development, and the results are one of the most brilliant in physics. Cavity cooling provides a really good platform for studying ultra-low temperature physics. In the re-cent years, extensive investigations on theoretical model, experiments and simulation of cavity cooling atoms are carried out. Models are established for the interaction between quantized laser field and the three-level atom. We discuss cavity cooling of the three-level atom by using semiclassical approach and quantum methods.Firstly, we briefly introduce the developing history of the laser cooling, looking back a series of ideas of the laser cooling and trapping for neutral atoms, some applications and the latest progress in laser cooling. Then, we introduce the basic theory of the two-level atom in an optical cavity. Based on these fundamentals, we focus on two parts due to the different methods.The contents of the semiclassical approach are as follows:Firstly, we research the cavity cooling of the three-level atom by using semiclassical approach-Maxwell's equations. In this chapter, on the one hand, we study theoretically of theⅤ-type three-level atom in a single mode cavity and show that the cooling rate can be increased by one order of magnitude than that of a two-level atom. On the other hand, we investigate the interaction between theΛ-type three-level atom and two mode cavity field, the cooling mechanism can be explained from the purely classical viewpoint and Sisyphus cooling mechanism. Secondly, the dynamical equations are obtained by a semiclassical approach, which is based on the joint atom- field Wigner function of both the motional atomic degrees of freedom and cavity field, including the spontaneous emission and cavity decay. The numerical results show that the cooling rate can be significantly improved by modulating parameters.The contents of the quantum methods are as follows:A theoretical study is carried out for the cavity cooling of theΞ-type three level atom and the A-type three-level atom in a high-finesse optical cavity, respec-tively. From the Hamiltonian of the atom-cavity system, making using of the rotating-wave approximation and in a frame rotating, we obtain the master equation of the system. Analytical expressions for the dipole force, the friction force and the friction coefficient are obtained by using the Heisenberg equations. Using the quantum regression theorem, we ob-tain the diffusion coefficient of the momentum. The achievable equilibrium temperature is given by the Einstein relation. We determine the detuning conditions for cavity cooling and heating regions by numerical calculations.We summary this thesis in the last chapter and outlook researches in the future.