中文摘要：

计算了四能级Tripd-型原子系统中探针光极化率随其频率失谐量的变化曲线。结果表明，当触发光作用于该系统的一个其振跃辽能级时，可使探针光的吸收和色散在其电磁感应透明（Electromagnetieally lnduced Transparency,EIT）窗口（由耦合光产牛）处发生显著变化。随着触发光Rabi频率的增加，探针光在EIT、窗口的吸收显著降低，色散显著增加。这种由触发光引起的探针光檄化率的变化对应着三阶Kerr非线性光学效应，这一效应在偏振量子相位门中有着潜在的应用价值。

英文摘要：

The susceptibility of the probe field in a four-level tripod-type atomic system as a function of the probe detuning is calculated. The results show that the absorption and dispersion of probe field near EIT resonance can be significantly changed while a trigger beam interacting with a transition in this system. With the increase of Rabi frequency of trigger beam, the absorption of probe beam at EIT window becomes smaller, and its dispersion becomes larger. Such changes of susceptibility of probe beam caused by a trigger beam are corresponding to the third Kerr nonlinearity, which have an application in polarization phase gate.