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 d 0 and d 10 configurations, we have developed a series of NLO vanadates A 4 MV 5 O 15 X including K 4 CdV 5 O 15 Cl, K 4 CdV 5 O 15 Br, Rb 4 CdV 5 O 15 Cl, and Rb 4 ZnV 5 O 15 Br. 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 Rb 4 ZnV 5 O 15 Br 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 A 4 MV 5 O 15 X a promising class of MIR NLO materials.