Mid Infrared Nonlinear Optical Series A 4 MV 5 O 15 X (A = K, Rb; M = Zn, Cd; X = Cl, Br) with Strong Second Harmonic Generation Responses

Mid infrared (MIR) nonlinear optical (NLO) crystals hold significant application values in academic and industrial fields. Here, by integrating cations with d⁰ and d¹⁰ configurations, we have developed a series of NLO vanadates A₄MV₅O₁₅X including K₄CdV₅O₁₅Cl, K₄CdV₅O₁₅Br, Rb₄CdV₅O₁₅Cl, and Rb₄ZnV₅O₁₅Br. These compounds exhibit strong SHG responses (1.28 to 1.40 × AGS @ 2.09 μm), broad transmission ranges (0.5 to 5.0 μm), and moderate band gaps (2.2-2.3 eV). Furthermore, these crystals except for Rb₄ZnV₅O₁₅Br exhibit congruent-melting characteristics, providing the potential for the growth of high-quality bulk single crystals. All of the intriguing physical properties make the family of A₄MV₅O₁₅X a promising class of MIR NLO materials.