随机激光形成于随机介质中局域模的放大,其放大特性依赖于局域模的空间分布。通过复折射率的虚部将光学增益引入系统,采用时域有限差分(FDTD)法,分析了增益介质中局域模的放大特性,并用模面积描述了局域模空间分布,着重对比分析了模面积对局域模放大特性的影响。模拟结果显示,局域模具有不同的空间分布,直接影响了局域模的放大特性,模面积较小的模式具有较低的损耗,能够获得更多能量,在介质中被优先放大,而模面积较大的模式,由于损耗较大,将获得较少的能量。

Random lasers result from the amplification of localized modes in random gain medium, and the amplification property depends on the spatial profile of the localized modes. Through the introduction of optical gain into system with an imaginary part of the complex refractive index, the amplification properties of localized modes are investigated by the finite-difference time-domain (FDTD) method. We find that different localized modes have different mode areas which have direct influence on the amplification property of the localized modes. The modes with smaller mode area undergo lower loss of energy than those with larger mode areas, so that they are amplified in advance while those modes with larger mode areas are suppressed due to mode competitions. This will lead to preferred amplification of the desired localized modes.