在四能级梯模型系统中通过两个连续相干场作用, 建立起基态和中间激发态之间的相干和粒子数转换。稳态条件下, 注入脉冲探测场, 通过受激拉曼作用, 获得较短波长的反斯托克斯激光信号。通过数值计算和理论分析, 得出获得最大频率转换效率的必要条件, 研究分析了两相干场的强度和探测场的脉宽、强度失谐等因素以及原子的各项参数对频率转换效率的影响。

A four-level ladder atomic system, driven by two continued fields, is considered. We show that higher coherence and population transfer can be created between the ground state and the meddle excited state. The short wavelength signal can be obtained by stimulated Raman effect when the probe pulse is imployed on the high excited state under steady condition. We show the condition for maximum frequency conversion efficiency by numerical simulation and theoretical analysis, and investigate the influences of the intensity of the two coherent fields,the pulsewidth, the detuning and the various parameters of the atoms on the frequency conversion efficiency.