Observation of Exceptional Stability in a Nonlinear Optical Crystal Under Extreme Conditions

Abstract As a unique nonlinear optical material, Ba 3 (ZnB 5 O 10 )PO 4 (BZBP) boasts a range of distinctive properties, including low anisotropic thermal expansivity, high specific heat, minimal walk‐off effect, large acceptance angle, non‐hygroscopicity, and high conversion efficiency. These features position BZBP as a highly promising candidate for crucial components in ultraviolet (UV) laser systems. Notably, all previous studies have been conducted under ambient pressures. In this research, synchrotron X‐ray diffraction and Raman spectroscopy are employed to investigate BZBP's behavior under extreme conditions. The findings revealed that BZBP remains exceptionally stable up to 43 Gigapascals (GPa), significantly extending its application range from ambient to high‐pressure environments. This stability enhancement opens new avenues for utilizing BZBP in optical systems designed to function under extreme conditions. Additionally, the study determined BZBP's bulk modulus (110 GPa) and linear compressibility along each lattice axis. Theoretical computations are used to assign the Raman modes, characterize their corresponding lattice vibrations, validate the experimental results, and elucidate the mechanisms underlying the material's remarkable stability.