Excitonic emission of monolayer semiconductors near-field coupled to high-Q microresonators

We present quantum yield measurements of single layer WSe₂ (1L-WSe₂) integrated with high-Q (Q>10⁶) optical microdisk cavities, using an efficient (>90%) near-field coupling scheme based on a tapered optical fiber. Coupling of the excitonic emission is achieved by placing 1L-WSe₂ to the evanescent cavity field. This preserves the microresonator high intrinsic quality factor (Q>10⁶) below the bandgap of 1L-WSe₂. The nonlinear excitation power dependence of the cavity quantum yield is in agreement with an exciton-exciton annihilation model. The cavity quantum yield is QY_c∼10⁻³, consistent with operation in the broad emitter regime (i.e. the emission lifetime of 1L-WSe₂ is significantly shorter than the bare cavity decay time). We discuss criteria for rigorous identification of lasing with layered materials.