Optimized arrangement of non-π-conjugated PO3NH3 units leads to enhanced ultraviolet optical nonlinearity in NaPO3NH3†
Abstract
The key to achieving nonlinear optical (NLO) crystals with superior optical properties lies in the development of new high-performance functional units and their precise arrangement. In this study, we identify the polar covalent tetrahedron (PO3NH3)−, with its remarkable optical properties, as a novel deep-ultraviolet (DUV) NLO-active unit for the first time. To ensure the (PO3NH3)− units are accurately aligned, we selected NaNH4PO3F·H2O as a template. Subsequently, we successfully synthesized NaPO3NH3, wherein the (PO3NH3)− units were arranged in an orderly manner. This excellent ordered arrangement of (PO3NH3)− units enables NaPO3NH3 to exhibit not only a significant SHG effect (1.2 × KDP), but also the largest birefringence (0.062@546.1 nm) among DUV non-π-conjugated phosphate systems.