Strong Nonlinear-Optical Response in the Pyrophosphate CsLiCdP₂O₇ with a Short Cutoff Edge

A high efficiency of laser-light conversion and short cutoff edge is essential to an ultraviolet (UV) nonlinear-optical (NLO) material. Previous researches on phosphates were mainly centered on alkali-metal or alkali-earth-metal phosphate systems, resulting in relatively weak NLO responses. Through the introduction of transition-metal cadmium and alkali-metal cesium elements with large radii into the phosphate system, a new UV NLO pyrophosphate, CsLiCdP₂O₇, has been synthesized. It exhibits a high second-harmonic-generation (SHG) efficiency of 1.5KH₂PO₄ and is transparent down to 200 nm. This work provides a new path for the design of UV NLO materials with high SHG efficiencies and short cutoff edges by introducing a transition metal with a d¹⁰ electron configuration and an alkali metal with a large radius into phosphate systems.