中文摘要：

数值计算具有自发辐射诱导相干性的开放V型三能级原子系统密度矩阵运动方程,分析无反转激光（LWI）增益的瞬态演化.结果表明：无论是否存在非相干抽运,探测场和驱动场间的相对位相（Ф）对增益的瞬态演化都有显著的影响;通过选择的取值可以获得更大的瞬态和稳定增益;不存在非相干抽运时,系统达到瞬态增益最大值及获得增益稳定值所需要的时间更长,演化过程中振荡幅度更大,获得的增益更大;原子退出速率r0（原子注入速率比S）的变化将使增益瞬态演化的具体过程发生改变,在r0（S）的一定取值范围内,瞬态和稳定增益随S（r0）的增大而增大.

英文摘要：

With numerical solution of density matrix motion equations of an open V-type three-level atomic system with spontaneously generated coherence, we analyze transient evolution of gain of lasing without inversion （LWI）. It is shown that relative phase （ Ф） between probe and driving fields has a significant effect on transient evolution of gain regardless of incoherent pump; Greater transient and steady gains can be obtained by selecting Ф; As incoherent pump is absent, longer time is needed to get the greatest transient gain and steady gain. Oscillation amplitude in the evolution process is greater, and gain is also greater; Changing atomic exit rate ro （ ratio of atomic injection rates S） leads to detail of gain transient evolution. In certain range of r0 （S）, transient and steady gains increase with S（ r0 ）.