Tunable resonant metasurfaces enabled by atomically thin semiconductors

Nanophotonics has recently gained new momentum with the emergence of a novel class of nanophotonic systems consisting of resonant dielectric nanostructures integrated with single or few layers of transition metal dichalcogenides (2D-TMDs). Thinned to the single-layer phase, 2D-TMDs are unique solid-state systems with excitonic states able to persist at room temperature, demonstrating notable tunability in the optical frequency range. Based on these properties, 2D-TMDs offer important opportunities for hybrid nanophotonic systems where a tailored nanostructure serves to enhance the light-matter interaction in the 2D-TMDs, while the 2D-TMDs can provide various active functionalities, thereby dramatically enhancing the scope of these hybrid systems. In this work, we combine 2D-TMDs with resonant metasurfaces composed of high-index dielectric nanoresonators. The dependence of excitonic states in 2D-TMDs on the charge carrier density leads to an amplitude modulation of the corresponding optical transitions as the Fermi level varies, thereby altering the coupling strength between the 2D-TMD and the resonant modes of the photonic nanostructure. We experimentally implement such a hybrid nanophotonic system and demonstrate voltage tuning of its reflectance as well as polarization-dependent behavior. Our results show that hybridization with 2D-TMDs can serve to render resonant photonic nanostructures tunable - an important property for practical applications, e.g., in optical analog computers and neuromorphic circuits.