Multicolor Ultralow‐Threshold Random Laser Assisted by Vertical‐Graphene Network

Abstract Application of lasers is omnipresent in modern‐day technology. However, preparation of a lasing device usually requires sophisticated design of the materials and is costly, which may limit the suitable choice of materials and the lasing wavelengths. Random lasers, on the other hand, can circumvent the aforementioned shortcomings with simpler fabrication process, lower processing cost, material flexibility for any lasing wavelengths with lower lasing threshold, providing a roadmap for the design of super‐bright lighting, displays, Li‐Fi, etc. In this work, ultralow‐threshold random laser action from semiconductor nanoparticles assisted by a highly porous vertical‐graphene‐nanowalls (GNWs) network is demonstrated. The GNWs embedded by the nanomaterials produce a suitable cavity for trapping the optical photons with semiconductor nanomaterials acting as the gain medium. The observed laser action shows ultralow values of threshold energy density ≈10 nJ cm −2 due to the strong photon trapping within the GNWs. The threshold pump fluence can be further lowered to ≈1 nJ cm −2 by coating Ag/SiO 2 upon the GNWs due to the combined effect of photon trapping and strong plasmonic enhancement. In view of the growing demand of functional materials and novel technologies, this work provides an important step toward realization of high‐performance optoelectronic devices.