Controlling Valley-Specific Light Emission from Monolayer MoS2 with Achiral Dielectric Metasurfaces

Excitonsin two-dimensional transition metal dichalcogenides havea valley degree of freedom that can be optically manipulated for quantuminformation processing. Here, we integrate MoS2 monolayerswith achiral silicon disk array metasurfaces to enhance and controlvalley-specific absorption and emission. Through the coupling to themetasurface electric and magnetic Mie modes, the intensity and lifetimeof the emission of neutral excitons, trions, and defect bound excitonscan be enhanced and shortened, respectively, while the spectral shapecan be modified. Additionally, the degree of polarization (DOP) ofexciton and trion emission from the valley can be symmetrically enhancedat 100 K. The DOP increase is attributed to both the metasurface-enhancedchiral absorption of light and the metasurface-enhanced exciton emissionfrom the Purcell effect. Combining Si-compatible photonic design withlarge-scale 2D materials integration, our work makes an importantstep toward on-chip valleytronic applications approaching room-temperatureoperation.