K4ZnV5O15Cl: A Congruent-Melting Mid-Infrared Nonlinear Optical Crystal Combined with Strong Second-Harmonic Generation and High Laser-Induced Damage Threshold

It is extremely challenging to accomplish second-harmonic generation (SHG) in the whole mid-infrared (MIR) region for oxide crystals due to their short IR absorption cutoff wavelengths. Herein, a new MIR nonlinear optical (NLO) crystal of K4ZnV5O15Cl (KZVC) is designed and synthesized by the aliovalent substitution of [(VO5)-O-III] with [(ZnO4Cl)-O-II] based on the K-2(VO)(V2O7) matrix. KZVC features an ordered 2D [ZnV5O15Cl](infinity) layered structure comprising [ZnO4Cl] / [VO5] square pyramids and [VO4] tetrahedron as functional units. Importantly, KZVC shows excellently balanced performances of strong SHG responses (12 x KDP @ 1064 nm, 1.1 x AgGaS2 @ 2.05 mu m), broad IR transparency range (0.52-10 mu m), congruent-melting behavior, and highest laser-induced damage threshold (LIDT) (60 x AgGaS2 @ 1064 nm) among the reported vanadates. Most remarkably, KZVC represents the first example in the oxide-based IR NLO crystals that can achieve phase matching in a wide wavelength range extending from 1.8 to 10 mu m, fully covering the important MIR atmospheric windows (3-5 mu m).