Low-Threshold and High Intensity Random Lasing Enhanced by MnCl2

Energy transfer is known to have a significant influence on random lasers. However, the study about the effect of energy transfer between metallic salt and dye molecules on random lasers is still lacking at present. Here, we investigate random lasing actions in Pyrromethene-597 (PM597), PM597-doped MnCl2 (manganese (II) chloride), PM597-doped polymer-dispersed liquid crystal (PDLC) and PM597-doped PDLC with MnCl2 capillary systems. We find that random lasing of the systems with MnCl2 exhibits lower threshold, higher intensity, sharper peak and variable resonance wavelength in comparison with the systems without MnCl2. This behavior is closely related to the decrease of fluorescence quenching effect and the enhancement of local field induced by energy transfer between MnCl2 and PM597. Red-shift of wavelength is observed with increasing dosage concentration of MnCl2 in the PM597-doped PDLC with MnCl2 system. Through the analysis of single-shot emission spectra of PM597-doped PDLC without and with MnCl2 systems, the role of MnCl2 in the coupling of lasing modes is confirmed. Lengths of laser oscillation cavities of the PM597-doped PDLC without and with MnCl2 systems are calculated by a power Fourier transform (PFT) analysis of their emission spectra. It well accounts for the effect of MnCl2 on the variation of the oscillation cavity.