Ca<sub>7</sub>(TeO<sub>3</sub>)<sub>6</sub>(MoO<sub>4</sub>): A Promising Mid-Infrared Nonlinear Optical Crystal Activated via a Module-Oriented Dimensionality Reduction Strategy
Tinghui Zhang, Fei Liang, Conggang Li, Ning Ye, Zhanggui Hu
Abstract
Nonlinear optical (NLO) materials are of fundamental interest in laser technologies, yet achieving high-performing NLO crystals remains a substantial challenge due to the inherent trade-offs in critical performance metrics. Here, we report a new quasi-zero-dimensional (0D) tellurite molybdate NLO crystal, Ca 7 (TeO 3 ) 6 (MoO 4 ) (CTMO), engineered via a module-oriented dimensionality reduction strategy. The identification of a record isolated Te–O to Mo–O group ratio of 6 in tellurite molybdates underscores an unparalleled structural configuration. Notably, CTMO exhibits the shortest UV cutoff edge of 266 nm accompanied by a record-breaking bandgap of 4.66 eV among all reported acentric molybdates, which endows CTMO with a high laser-induced damage threshold 42 times higher than that of AgGaS 2 . Moreover, it demonstrates the strongest second harmonic generation (SHG) response of approximately 8.6 × KDP among molybdates with bandgaps exceeding 4 eV, a desirable birefringence value of 0.092@1064 nm for an effective phase matching process, and an extended IR absorption edge beyond 7.0 μm. Structural and theoretical analyses reveal that the well-balanced activities of CTMO arise from the synergistic effects of densely packed [TeO 3 ] trigonal pyramids and well-aligned [MoO 4 ] modules. The discovery of CTMO facilitates the utilization of acentric oxides as mid-IR NLO crystals, and it provides a straightforward and effective approach toward the rational design of novel NLO crystals with enhanced overall performance.