铷原子耦合光频率近共振时的电磁感应透明∗

摘要

研究了Λ型能级系统中,85Rb原子在耦合光频率失谐较小时的电磁感应透明(EIT)现象。实验中,随着耦合光频率失谐量的增加,电磁感应透明窗口的绝对强度有所减弱,但是其相对深度却有所增加,透明窗口相对深度最大的位置不在耦合光频率共振处,而是在耦合光频率失谐约180 MHz的位置。用三能级和四能级系统的理论分别对实验结果进行对比分析,发现用四能级系统的理论进行拟合的结果与实验符合得比较好。对此,我们提出当耦合光频率失谐较小时, EIT信号是两个激发态共同作用的结果,并用四能级系统的理论分析了两个激发态之间的能级间隔对透明窗口相对深度最大值位置的影响。%The phenomenon of electromagnetically induced transparency (EIT) in 85Rb atomic vapor is studied in a Λ-type of four-level system with the coupling laser frequency detuned from the atomic resonance frequency. We find that the EIT intensity grows weaker as the coupling laser frequency is detuned from resonance, but the relative depth of the transparency window increases. The maximum depth appears when the coupling frequency is detuned at about+180 MHz, not at the resonance frequency. We demonstrate that this is a result of the combined effect of the two excited states, and present a theoretical analysis based on the four-level system, which agrees quite well with the experimental results.