Efficient All-Optical Plasmonic Modulators with Atomically Thin Van Der Waals Heterostructures.

All-optical modulators are attracting significant attention due to their intrinsic perspective on high-speed, low-loss, and broadband performance, which are promising to replace their electrical counterparts for future information communication technology. However, high-power consumption and large footprint remain obstacles for the prevailing nonlinear optical methods due to the weak photon-photon interaction. Here, efficient all-optical mid-infrared plasmonic waveguide and free-space modulators in atomically thin graphene-MoS heterostructures based on the ultrafast and efficient doping of graphene with the photogenerated carrier in the monolayer MoS are reported. Plasmonic modulation of 44 cm is demonstrated by an LED with light intensity down to 0.15 mW cm , which is four orders of magnitude smaller than the prevailing graphene nonlinear all-optical modulators (≈10 mW cm ). The ultrafast carrier transfer and recombination time of photogenerated carriers in the heterostructure may achieve ultrafast modulation of the graphene plasmon. The demonstration of the efficient all-optical mid-infrared plasmonic modulators, with chip-scale integrability and deep-sub wavelength light field confinement derived from the van der Waals heterostructures, may be an important step toward on-chip all-optical devices.