Low-Threshold Lasing of Interlayer Excitons in Freestanding TMD Heterostructures.

Transition metal dichalcogenides (TMDs) have recently emerged as attractive material candidates for advanced photonic applications. Due to their atomically thin thickness, TMD monolayers can be intimately integrated into optical cavities, enabling excitonic lasers with miniaturized and highly versatile device architectures. TMD heterostructures, combining two dissimilar monolayers into single devices, have also been intensively investigated, presenting the potential of interlayer exciton lasers with high tunability and ultra-low lasing threshold. However, the spatially indirect nature of interlayer excitons with reduced emission intensity has posed a major challenge for achieving efficient lasing behaviors in TMD heterostructures. In this study, we employ the freestanding geometry of cavity-coupled TMD materials, significantly enhancing the interlayer exciton emission intensity and decreasing the lasing threshold. The onset of the interlayer exciton lasing operation was observed at a threshold of 75 nW, which was considerably lower than the supported structure. Our results show the potential of dielectric engineering of interlayer-exciton-coupled microcavity lasers for the development of low-power-consumption coherent light sources for integrated quantum photonics.