Electronic paramagnetic resonance analysis of point defects in lithium niobate: progress and prospects

Lithium niobate (LiNbO₃) crystals, renowned for their exceptional piezoelectric, electro-optic, and nonlinear optical properties, are indispensable in photonic applications such as optical communication, integrated optics, and laser technology. However, the performance of LiNbO₃-based devices is fundamentally limited by point defects. Consequently, elucidating the mechanisms underlying point defect formation and achieving precise control over defect engineering have emerged as critical research priorities. Although conventional characterization techniques face inherent limitations in directly resolving the microstructures of point defects, electron paramagnetic resonance (EPR) spectroscopy has proven to be a pivotal analytical tool for the non-destructive characterization of paramagnetic defects, driving significant advancements in LiNbO₃ defect research. This article summarizes the intrinsic and impurity defects that significantly affect the optoelectronic properties of LiNbO₃ crystals. Firstly, it elucidates the primary types of point defects, their microstructural characteristics, and their impacts on material properties. Subsequently, it highlights the advancements in EPR technology for studying point defects and provides an in-depth analysis of its advantages in defect analysis. Finally, it proposes the future concerns of studying point defects in LiNbO₃ crystals using EPR technology.