Analysis of ZnO Random Laser Spectra under Nanosecond Pumping

摘要

Early observed peculiarities of ZnO random laser spectra are analyzed. By simplified simulation of lasing time behavior it is shown that plausible origin of lasing spectra variations from shot to shot can be the fluctuations of the number of spontaneous photons that can serve as a "seed" for laser effect creation in a certain mode. Such fluctuations are very significant for spatially overlapping modes. Analysis of a statistics of different line appearance in the lasing spectra showed that the number of lasing modes in monodisperse sample is less than in polydisperse ones. This finding can explain why lasing spectra variations are more pronounced in polydisperse samples. We associate observed large line widths with the existence of several lasing acts during every pumping shot and with the slight changes of some modes frequencies in the course of each lasing act. Preliminary experimental result confirms such supposition.