Efficient Lasing in MoS$_2$/WSe$_2$-Based Metasurfaces Enabled by Quasi-Dark Magnetic Dipole Resonance

The novel combination of a strongly-resonant optical metasurface with the MoS$_2$/WSe$_2$ hetero-bilayer is proposed for efficient free-space lasing enabled by the enhanced coupling between the optical and matter (exciton) states. The metasurface comprises silicon-rich nitride meta-atoms periodically arrayed in a subdiffractive lattice and overlaid with MoS$_2$/WSe$_2$, which provides optically-pumped gain around $1130~\mathrm{nm}$. Light emission is enabled by exploiting a quasi-bound state in the continuum in the form of a perturbed vertical magnetic dipole resonance. Following a meticulous design process guided by full-wave simulations and multipole expansion analysis, an ultralow lasing threshold of $\sim 6~\mathrm{kW/cm^2}$ is achieved. Moreover, the thermal stability of the lasing structure is examined through heat transfer simulations; stable operation with pump power densities up to a few MW/cm$^2$ (three orders of magnitude above the threshold) is predicted. These results demonstrate that MoS$_2$/WSe$_2$-based metasurface lasers can exhibit robust operation, paving the way for highly-performing ultrathin light-emitting surfaces. The lasing response is rigorously assessed through a highly-efficient temporal coupled-mode theory framework, verified by time-domain FEM simulations showing excellent agreement. Thus, an efficient and accurate approach to design and study metasurface lasers with arbitrary geometries and surface or bulk gain media is introduced, exhibiting significant advantages over cumbersome full-wave simulations.