Spectral behavior of partially pumped weakly scattering random lasers.

Stochastic noise is incorporated in the numerical simulation of weakly scattering random lasers, which qualitatively captures lasing phenomena that have been observed experimentally. We examine the behavior of the emission spectrum while pumping only part of the entire one-dimensional random system. A decrease in the density of lasing states is the dominant mechanism for observing discrete lasing peaks when absorption exists in the unpumped region. Without such absorption, the density of lasing states does not reduce as dramatically but the statistical distribution of (linear) lasing thresholds is broadened. This may facilitate incremental observation of lasing in smaller-threshold modes in the emission spectrum with fine adjustments of the pumping rate.