A Band‐Orientation Co‐Anchoring Strategy for the Design of a High‐Performance Mid‐Infrared Nonlinear Optical Crystal

Abstract Mid‐infrared (MIR) nonlinear optical (NLO) crystals have long been pursued, yet the realization of a balance among key performance metrics remains a formidable challenge. Herein, we propose a band‐orientation co‐anchoring strategy to precisely regulate the band structures and module spatial arrangement for the rational design of high‐performance MIR NLO crystals. Leveraging the deep‐ultraviolet NLO KBe 2 BO 3 F 2 (KBBF) as a template, a novel MIR NLO Rb 3 ZnV 4 O 12 Br (RZVB) crystal was successfully obtained through multimodule substitution. Importantly, the tailored tetrahedral hybridization mode effectively anchors the conduction band minimum—dominated by d 0 cations—at a higher energy level and suppresses d–d transitions. Concurrently, structural confinement within the KBBF‐derived lattice enforces the optimal alignment of distorted tetrahedra. Furthermore, RZVB displays an unprecedented second harmonic generation (SHG) enhancement mechanism, arising from a unique cross‐module electron transfer. Consequently, RZVB exhibits superior linear and NLO performances, including a wide bandgap (3.25 eV), high laser threshold damage (1.07 GW/cm 2 @1064 nm), broad transmission window (0.382–7.6 µm), moderate birefringence (0.06@589.3 nm) and the strongest SHG response (7.7 × KDP@1064 nm and 1.45 × AGS@2.09 µm) among vanadates with bandgap exceeding 3 eV. This work presents a high‐performance MIR NLO crystal and establishes a bottom‐up, broadly applicable design paradigm for the tailored development of next‐generation crystalline materials.