在非旋波近似下,研究了频率随时间变化的相干态光场与二能级原子的相互作用,讨论了光场频率随时间作正弦和方波变化时,原子布居数反转随时间的演化特性。数值计算结果表明,当光场频率不随时间变化时,原子布居数反转的周期随着平均光子数的增大而增大;当光场频率随时间作正弦变化时,原子布居数反转塌缩回复的周期和振幅受到了很大影响,光场频率对演化曲线的振荡频率起到了调制作用;当光场频率随时间作方波变化时,原子布居数反转塌缩回复的周期发生了改变,而且出现了新的塌缩回复现象。

The interaction between a coherent state light field with time-varying frequency and two-level atoms is investigated under non-rotating-wave approximation. The time evolution of the atomic population inversion is discussed when the field frequency changes with time in a sine or a square wave way. The numerical results indicate that, when the light field frequency does not change with time, the period of atomic population inversion increases with the increase of the mean photon number. When the field frequency changes with time in a sine wave way, the collapse-revival period and the amplitude of atomic population inversion are strongly affected, and the frequency of the light field plays a modulation role in the oscillation frequency of evolution curves. When the field frequency changes with time in a square wave way, the collapse-revival period of the atomic population inversion changes and a new collapse-revival phenomenon emerges.