Generation of Silver Metal Nanocluster Random Lasing

Atomically precise molecular-like metal nanoclusters (MNCs) exhibit unique properties, such as strong photoluminescence and absorption with inherent biocompatibility, which enable us to extend their applications to chemical sensing, biomedical imaging, optoelectronics, and many other areas. However, stimulated laser emission is greatly desirable to upgrade their more advanced functionalities. Here we provide a plausible approach to achieve this outstanding characteristic from MNCs. Quite interestingly, by integrating hyperbolic metamaterials (HMMs) with highly luminescent silver metal nanoclusters (Ag-TSA MNCs), a strong stimulated emission (random lasing action) with a low threshold of ∼0.5 kW cm-2 is discovered. The light emission is enhanced by ∼35 times when the solid-state assembly of Ag-TSA MNCs is integrated with HMM in comparison with that with a silicon substrate. The high-k modes excited by the HMM offer the possibility of forming the coherent closed feedback loops necessary for random lasing actions, thereby decreasing the energy loss associated with the photons' propagation in the matrix. The simulations derived from the finite-difference time-domain method support the experimental results. Our study shown here makes an initial step to demonstrate stimulated laser action from metal nanoclusters. It is believed that there exist many other alternatives for exploring this emerging research topic for the future development of cost-effective and biocompatible optoelectronic devices.