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

We present quantum yield measurements of single layer ${\text{WSe}}_2$ (1L-${\text{WSe}}_2$) integrated with high-Q ($Q>{10}^6$) optical microdisk cavities, using an efficient ($\eta >$90%) near-field coupling scheme based on a tapered optical fiber. Coupling of the excitonic emission is achieved by placing 1L-WSe${}_2$ to the evanescent cavity field. This preserves the microresonator high intrinsic quality factor ($Q>{10}^6$) below the bandgap of 1L-WSe${}_2$. The nonlinear excitation power dependence of the cavity quantum yield is in agreement with an exciton-exciton annihilation model. The cavity quantum yield is ${\text{QY}}_{\text{c}}\sim {10}^{-3}$, consistent with operation in the $\mathit{\text{broad}}\mathit{\text{emitter}}$ regime (i.e. the emission lifetime of 1L-WSe${}_2$ is significantly shorter than the bare cavity decay time). This scheme can serve as a precise measurement tool for the excitonic emission of layered materials into cavity modes, for both in plane and out of plane excitation.