Second‐Harmonic and Third‐Harmonic Generations in2DLayered Materials

Atomically thin 2D layered materials (2DLMs) have received considerable attention in recent years because of their unique optical, electrical, and photoelectrical properties when charge transport is confined to a plane. Most recently, the nonlinear optical (NLO) properties of 2DLMs are intriguing for the fundamental science point of view and various potential applications. Here, the current state of the art in the field of second-harmonic generation (SHG) and third-harmonic generation (THG) based on 2DLMs is reviewed. In particular, the criteria of chiral selection rules for the harmonic generations (HG) and different strategies to tune SHG and THG in 2DLMs are also discussed. Several open areas of potential perspectives and research possibilities of these promising 2DLM-based SHG and THG are also presented. It is believed that HG in 2DLMs will provide meaningful guidance for novel NLO devices in the future.