Ca₇(TeO₃)₆(MoO₄): A Promising Mid-Infrared Nonlinear Optical Crystal Activated via a Module-Oriented Dimensionality Reduction Strategy

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, Ca₇(TeO₃)₆(MoO₄) (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 AgGaS₂. 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 [TeO₃] trigonal pyramids and well-aligned [MoO₄] 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.