Influence of fiber and MnCl_2 on mode and threshold of random lasing in random gain systems

A mode and threshold tunable random laser assisted by MnCl2 and fiber is investigated. This is constructed by doping MnCl2 with different concentrations and embedding fiber in the dye Pyrromethene-597(PM597)-doped negative liquid crystal (NLC) glass capillary samples. The excellent overlap of the absorption spectrum of MnCl2 with both the fluorescence and absorption spectra of dye PM597 provides the low threshold and tuning properties for the random lasing. The low-threshold and fewer-mode peculiarity of the random lasing for the systems with fiber is attributed to longer photon residence time provided by the fiber in the random gain-scattering systems. The simple and straightforward approach of random lasing control holds potential to enable optical device fabrication based on random lasers.