Crescent-shaped shadow of second harmonic generation in dielectric microsphere/TMD monolayer heterostructure

Abstract For heterointerfaces at micro/nano scales, extremely-space-confined second harmonic generation (SHG) of transition metal dichalcogenide (TMD) monolayers can facilitate the extraction of TMD monolayers’ 3D dielectric environment. Here, we construct SiO 2 microsphere/MoS 2 monolayer (3D/2D) heterostructures and spatially resolve their SHG distributions via pixel-to-pixel spatial mapping. Asymmetric 3D refractive index distribution of the microsphere is successfully projected to 2D plane of TMD monolayer and visualized by corresponding 2D image of SHG intensity distribution, which presents a crescent-shaped shadow. Out results open up new possibilities for 3D interfacial sensing and imaging with SHG of 2D monolayers.