采用了一个梯形四能级原子系统，在多模光场的作用下利用量子相干技术使其实现介质的左手效应，使介质具备左手材料特性。在相互作用表象下，利用密度矩阵方程并结合相关条件下的有关公式进行理论计算，数值模拟结果显示，在合适的参量条件下，介质的相对介电常量和相对磁导率可以同时出现负值，产生了左手效应，相应的介质转化为左手材料。通过讨论在左手效应成立的条件下介质对光场的吸收和增益问题，结果表明，在弱探测场条件下，利用电磁诱导的方法也可以实现介质的左手效应。

The system of a ladder-type four-level atoms interacting with multi-mode light fields is discussed to possess left handedness through the mechanism of quantum interference. In the representation of interaction, the density matrix method is utilized. The conclusion of the numerical simulation shows that to use appropriately chosen parameters, the real parts of both the relative dielectric permittivity and the relative magnetic permeability will be negative, and then the left handedness effect happens and the left-handed material is realized. The medium to affect light absorption and gain in the conclusion of the establishment of left-handed effect are also discussed. The results show that in the condition of weak probe field, the electro-magnetic induction can be used to achieve the left-handed effect of the medium.