High-harmonic generation (HHG) in graphene heterostructures, consisting of metallic nanoribbons separated from a sheet by either few-nanometer layer aluminum oxide or an atomic monolayer hexagonal boron nitride, is investigated. The amplify the near-field at relative to externally applied pumping, thus allowing observation third- and fifth-harmonic carbon modest pump powers mid-infrared. depend...

Implementing nonlinear optical components in nanoscale photonic devices is challenged by phase-matching conditions requiring thicknesses the order of hundreds wavelengths, and disadvantaged short interaction depth nanometre-scale materials weak photon–photon interactions. Here we report that ferroelectric NbOI2 nanosheets exhibit giant second-harmonic generation with conversion efficiencies are...