Fabrication of a dye-based random laser using ZnS:Mn quantum dots and investigating the effects of their concentration

Zinc chalcogenide quantum dots (QDs) doped with paramagnetic transition metal ions (particularly ZnS:Mn QDs) are new attractive but rarely examined semiconductor nanocrystals that have excellent optical properties and enhanced thermal and environmental stability compared to Cd-based QDs. In this paper, we demonstrate a dye-based random laser (RL) with nonresonant feedback using ZnS:Mn QDs as the scattering medium that are dispersed in a Rhodamine B (RhB) dye solution. The nonlinear variation of the emission spectrum as a function of the excitation energy implies a random lasing threshold. Moreover, we observe a blue-shift of the emission wavelength by 10.3 nm and a 5.3 times decrease in the RL threshold by increasing the scatterer concentration. We also provide a theoretical discussion based on the diffusion theory for explaining the observed experimental results.