▎ 摘　　要

The nonlinear optical properties of van der Waals bilayer heterostructures composed of graphene/h-BN and graphene/phosphorene nanoflakes are investigated using time-dependent density functional theory. Our calculated results show a significant enhancement of the first-hyperpolarizability value, beta in heterostructures relative to the pristine nanoflakes at lambda = 1064 nm. The calculated enhancement in optical nonlinearity mainly results from in-plane anisotropy induced by the interlayer electronic coupling between the adjacent nanoflake layers; a higher degree of anisotropy is induced by puckered phosphorene compared to atomically flat h-BN yielding chi((2)) value corresponding to the second harmonic generation of similar to 50 pm V-1 in the zigzag graphene/phosphorene bilayer heterostructure. The calculated results clearly show that graphene-based nanoflake heterostructures giving large NLO coefficients together with high electron mobility of these materials offer new opportunities as candidate materials of choice for next-generation photonics and integrated quantum technologies.