∧型四能级系统中的多重电磁诱导光透明研究

运用密度矩阵理论，研究了在外加相干耦合场作用下∧型四能级系统的吸收和色散特性。数值模拟表明：通过调节外加相干场的拉比频率强度，该系统可以单重、双重电磁诱导光透明现象，并在缀饰态表象中给出了定性解释。在双重电磁诱导透明现象中，透明窗的位置和吸收峰值可以通过调节外加相干场的失谐量来进行控制，而且透明点的位置可以连续变化。每个透明窗口在吸收最低时都伴随着高折射率，因此可以在此介质中实现超光速传播。

Multiple Electromagnetically Induced Transparency in a Four-Level Atomic System

Using matrix theory, the absorption and dispersion properties of a lamda-type four-level system driven by two coherent fields are investigated. The result obtained hy means of numerical method indicates that hy adjusting the intensity of Rabi frequencies of the coherent field in the steady state, double or single electromagnetically induced transparency （EIT） can appear explicitly in this system. And the explanations of these phenomena are given by using the dressed states. In the double electromagnetically induced transparency, the location of transparent windows can be manipulated by controlling the detuning of the driving field. Additionally, it is also found that the medium shows a large refractive index at each transparency window, and the group velocity of the probe laser can be enhanced.