Highly efficient interlayer exciton microcavity laser in free-standing 2D Heterostructures

Monolayer transition metal dichalcogenides (TMDs), such as molybdenum diselenide (MoSe₂) and tungsten diselenide (WSe₂), are direct gap semiconductors with strong excitonic features which can be potentially useful for various optoelectronic applications. When integrated with optical cavities, monolayer TMDs have shown not only the enhancement of the spontaneous emission but also the stimulated emission beyond the lasing threshold. By coupling a stacked TMD hetero-bilayer with optical cavities, unique advantages of excitonic lasers have been reported such as the high tunability of interlayer exciton emission and the low threshold of lasing operation. In this study, we demonstrate highly efficient lasing from interlayer excitons in a WSe₂/MoSe₂ hetero-bilayer through integration with a silica microsphere. Using a high Q (~2600) cavity and prepatterned hole substrates, we significantly enhance the emission of interlayer excitons and modify the lifetime, achieving an ultra-low lasing threshold of 75 nW. The measured resonance peaks were in good agreement with finite-difference time-domain (FDTD) simulation results. These findings highlight the potential of van der Waals heterostructures for the development of microcavity lasers, paving the way for low-power and highly efficient optical components in quantum photonic applications.