Dynamic Metasurfaces Based on a Tunable Material Resonance in High-Quality, Large-Area 2D Semiconductors

Dynamic tuning of metasurfaces raises many potential applications. Such tuning can be achieved by changing either the material or geometric properties of the metasurface building blocks. In particular, two-dimensional transition metal dichalcogenides (2D TMDCs) are of interest as a novel material platform to integrate with metasurfaces. At atomic-layer limit, the possibility to excite excitons offers a strong “Materials Resonance” that can efficiently couple to the geometric resonances of dielectric and plasmonic nanostructures. The strength of excitonic resonance and its spectral location can be effectively controlled by methods such as electrical gating, material strain and dielectric screening. Such modulation can be harnessed to induce large changes in the optical material properties. However, the availability of high-quality, large-area 2D TMDCs is still limited by current synthesis and exfoliation methods and can be impacted by large-area patterning techniques.<br/><br/>Here we present optical tunable antennas and metasurfaces combing large-area monolayer/hetero-bilayer TMDCs and plasmonic structures. We show how intralayer/interlayer excitons can couple with plasmonic resonators and provide emission that is polarized in-/out-of-plane respectively and is controlled by solid-state electrical gating. With an Au-assisted large-area exfoliation method, we achieve scalable optoelectronic devices capable of amplitude, phase and propagation control. By applying 0.5V/nm bias across a gate oxide and electrically doping monolayer WS₂, we can reversibly and fully quench the excitonic resonance at 615nm. We further functionalize the plasmonic-assisted 2D emitters at room temperature, which not only enhances the light-matter interaction, but also actively redirects the photoluminescence from a patterned monolayer WS₂. We also demonstrate that interlayer excitons existing in device-scale hetero-bilayer TMDCs can be directly imaged and manipulated by judicious design of plasmonic antennas. Combining both in- and out-of-plane control in scalable TMDCs will open a promising avenue for tunable nanophotonic devices and metasurfaces.