The Origin of Threshold Reduction in Random Lasers Based on MoS[sub.2]/Au NPs: Charge Transfer

Random lasers have attracted much attention in recent years owing to their advantages of a simple fabrication process, low processing cost, and material flexibility for any lasing wavelengths. They provide a roadmap for the design of ultra-bright lighting, displays, etc. However, the threshold reduction in random nanolasers remains a challenge in practical applications. In this work, lower-threshold random laser action from monolayer molybdenum disulfide film-encapsulated Au nanoparticles (MoS[sub.2]/Au NPs) is demonstrated. The observed laser action of the MoS[sub.2]/Au NPs shows a lower threshold of about 0.564 µJ/mm[sup.2], which is about 46.2% lower than the threshold of random lasers based on Au NPs. We proposed that the charge transfer between MoS[sub.2] and the gain material is the main reason for the reduction in the random laser threshold. The finite-difference time-domain (FDTD) method was used to calculate the lasing action of these two nanostructures. When charge transfer is taken into account, the theoretically calculated threshold of the MoS[sub.2]/Au NPs is reduced by 46.8% compared to Au NP samples, which is consistent with the experimental results. This study provides a new mechanism to achieve low-threshold and high-quality random lasers, which has the potential to facilitate the application of random lasers and the development of high-performance optoelectronic devices.