A promising van der Waals two-dimensional nonlinear optical crystal NbOCl_(2) for ultrathin quantum light source

Nonlinear optical(NLO)crystals are the key fundamental materials in modern optoelectronic information technology,which play an irre-placeable role in modern quantum optics and photonics in addition to traditional laser frequency conversion applications[1,2].Especially at a time when the international competition of quantum information tech-nology is becoming increasingly intense,high-performing NLO crystals as the strategic materials for optical quantum technology have received continuous attention from physical chemists and materials scientists.