中文摘要：

基于非相干反馈随机激光器的扩散方程理论，将扩散方程中的增益项改写为饱和形式，并利用有限差分方法，研究了双光子抽运随机激光器中辐射光能量随时间演化特性．对扩散方程的数值求解给出了系统辐射光能量由自发辐射开始，经历小信号增益状态得到放大，再到由于增益饱和形成稳态输出的整个演化过程．表明介质的无序导致了在较低能量情况下也能获得饱和增益这样的非线性效应．结果为研究获得双光子抽运随机激光器的稳态输出提供了理论依据．

英文摘要：

Based on the diffusive equation of incoherent-feedback random lasers, whose gain is modified by adding a saturation factor, the evolution of the emitted light intensity in two-photon pumping random lasers varying with time is studied by use of finite difference method. Numerical results show how the intensity of emitted light varies from the spontaneous radiation, which undergoes amplification at small-signal gain, to the steady output due to the saturation effect. It is noted that the nonlinear effect, e.g. saturation of gain,in such laser system can be achieved under low intensity conditions due to the disorder of media. Our results give a theoretical support to obtaining the steady output of the two-photon pumping random lasers.