【作者】 陈险峰；

【导师】 朱士群；

【作者基本信息】 苏州大学 ， 光学， 2001， 硕士

【摘要】 在激光冷却与囚禁中，需要对作用在原子上的压力进行研究。一般说来，可从两能级原子出发，将多能级原子进行简化，来分析激光场与原子相互作用时原子的受力情况。 在本文中，我们从半经典理论出发，利用光学布洛赫方程，考察与激光驻波场相互作用的两能级原子上的受力情况。结果表明，当选择负失谐量时，原子将受到来自光场的阻滞力，在此阻滞力的作用下，原子的速度大大减小，温度降低，出现冷却效应。当光强比较弱时，作用在原子上的力为洛仑兹型。而当光强较强时，依赖于速度的零阶力在零速度附近方向发生了反转，出现了扭结现象。 随着场强的增大，力的高阶谐波项随着场强的增大而增大，而且偶次高阶项的作用与零阶项的作用相同，奇次项的作用与此相反。虽然在高强度时力的奇、偶高阶项的整体作用往往大部分相互抵消，但这与弱场强时高阶谐波项的作用可以忽略相比存在很大的差异。更多还原

【Abstract】 Abstract In laser cooling and trapping, the controllable force on the atom needs to be investigated. Usually, from a two-level atom, the multi-level atom can be simplified. The force acting on the atom can be analysed when the laser field interacts with the atom. In this thesis, a semiclassical model of the force on an atom is used to describe the motion of a two-level atom interacting with a standing-wave laser field. The velocity dependent force is derived through optical Bloch equations. It is shown that a negative detuning of the laser field from the atomic resonance would lead to nonzero light pressure forces and reduce velocities along the laser beam axis. When the intensity of the laser field is weak the velocity dependence of the average longitudinal force has the Doppler-shifted lorenztian resonance. At high intensities, there is a kink and change of direction of the light pressure force near the point of zero velocity. When the intensity of the laser field increases, the effects of the higher order harmonic light pressure forces become significant. It is seen that the behaviors of light pressure forces with even order are similar to the zero order force while that of odd order forces are opposite to the zero order one. Though the whole effects of the odd order and even order harmonic forces are almost destructive with each other for strong intensity, it is quite different compared to the case of weak intensity. For weak intensity, the higher order harmonic forces can be neglected.更多还原