Radiation-induced defects in lithium niobate crystals: Mechanisms and implications for space-borne electro-optic devices

LiNbO3 (lithium niobate) crystals, due to their excellent electro-optic properties, have significant potential applications in spacecraft electro-optic field measurements and space laser communication systems. However, the performance degradation mechanisms of LiNbO3 in space radiation environments remain unclear, which has become a key bottleneck limiting its space applications. This study, combining first-principles calculations with experimental verification, systematically investigates the space radiation effects on LiNbO3 crystals. By constructing intrinsic and defect-containing (such as anti-niobium sites, lithium vacancies, etc.) LiNbO3 crystal models, the impact of gamma-ray irradiation on their optical properties was analyzed. The simulation results show that the anti-niobium site defect (NbLi4+) significantly reduces the crystal bandgap (from 3.564 to 2.453 eV), leading to an increased absorption coefficient in the visible light range (350–1550 nm), while the refractive index changes slightly (Δno < 0.09‰, Δne < 0.8%). Experimental results further validate these findings: under a 500 krad irradiation dose, the crystal absorption indices ko and ke increased by 27.6% and 12.6%, respectively, while the refractive index only showed minor fluctuations. The study indicates that radiation-induced anti-niobium site defects are the dominant factor in optical performance degradation, affecting the absorption characteristics by altering the O2− → Nb5+ charge transition path. This research provides theoretical and experimental support for optimizing the performance of LiNbO3 crystals in space radiation environments and holds significant importance for the design of high-reliability aerospace optoelectronic materials.