Recent development of lithium niobate-based luminescent materials for photonics and optoelectronics

Lithium niobate (LiNbO₃) is a key material in photonics and optoelectronics, valued for its ferroelectric, electro-optic, and nonlinear optical properties. Despite its high Curie temperature and significant spontaneous polarization, which are advantageous for light modulation and frequency conversion, undoped LiNbO₃ suffers from intrinsically weak luminescence, thereby restricting its application in light-emitting devices. Doping with rare earth ions such as erbium (Er³⁺), neodymium (Nd³⁺), and praseodymium (Pr³⁺) significantly enhances its luminescent properties by introducing efficient photon-emitting energy levels. This review provides a comprehensive overview of the luminescent properties of pure and doped LiNbO₃, with a particular focus on doping and co-doping strategies using rare earth and transition-metal ions to enhance their photoluminescence efficiency, thermal stability, and spectral tunability. The roles of dopant site occupancy, defect engineering, and charge compensation mechanisms are discussed in detail. Co-doping approaches are highlighted as promising routes to synergistically tailor emission characteristics and mitigate concentration quenching. Furthermore, the review explores recent advances in LiNbO₃-based luminescent devices, including waveguide-integrated photonic components, resonators, and thin films. Finally, future challenges and perspectives are outlined for the rational design of high-performance LiNbO₃-based luminescent materials in next-generation photonic technologies.