中文摘要：

详细研究了Λ型三能级原子系统中电磁感应透明的瞬态过程。我们从理论上分析了系统中各参数（例如失谐、原子能级衰减率、探测场和耦合场强度）对瞬态响应时间的影响,并且通过对密度矩阵演化方程的数值求解,分析了相关密度矩阵元尤其是与吸收和色散相关的矩阵元ρab的瞬态行为。结果发现：在满足双光子共振条件Δ=Δμ的情况下,瞬态响应时间与能级衰减速率以及探测场和原子跃迁的失谐有直接关系;随着失谐的增大,响应时间也相应延长,同时,瞬态响应时间也随着衰减率γ的增大而缩短。而探测场和耦合场的强度变化并未对响应时间造成影响。此外,很多文献都指出,常用的微扰近似稳态解只适用于探测场强度远小于耦合场强度的情况,而本文则通过对比数值解的稳定值和微扰近似稳态解的差异,给出了其适用的确切范围：即应满足PE/h≤0.1Ωμ。

英文摘要：

In this paper the transient behavior of electromagnetically induced transparency in three-level A- type atomic systems was investigated in detail. We analyzed theoretically the influence of the system parameters （i. e. detuning,decay rate,strength of external field） on the transient responsing time and the transient behavior of corresponding density matrix element especially for pab via exact numerical calculation. The results show that the responsing time has a direct relation to the decay rate and the detuning between the driven and probe fields. Choosing a suitable environment of larger decay rate can significantly shorten the responsing time. Meanwhile, the transient process should be prolonged when adopted detuning probe field and the responsing time is insensitive to the strength of driven and probe fields. The limitation on the relative strength of probe field to the driven field, which is suitable for the usual approximation steady-state theory, was also discussed. And we find the limit intensity of the probe field in the approximate solutions is PE/h≤0.1Ωμ.