  Moir\'e superlattices in van der Waals heterostructures offer highly tunable
quantum systems with emergent electronic and excitonic properties such as
superconductivity, topological edge states, and moir\'e-trapped excitons.
Theoretical calculations predicted the existence of the moir\'e potential at
elevated temperatures; however, its impact on the optical properties of
interlayer excitons (IXs) at room temperature is lacking, and the benefits of
the moir\'e effects for lasing applications remain unexplored. We report that
the moir\'e potential in a molybdenum disulfide/tungsten diselenide (MoS2/WSe2)
heterobilayer system can significantly enhance light emission, elongate the IX
lifetime, and modulate the IX emission energy at room temperature. By
integrating a moir\'e superlattice with a silicon topological nanocavity, we
achieve ultra-low-threshold lasing at the technologically important
telecommunication O-band thanks to the significant moir\'e modulation.
Moreover, the high-quality topological nanocavities facilitate the highest
spectral coherence of < 0.1 nm linewidth among all reported two-dimensional
material-based laser systems. Our findings not only open a new avenue for
studying correlated states at elevated temperatures, but also enable novel
architectures for integrated on-chip photonics and optoelectronics.
