MgO-doped LiNbO3 is a groundbreaking advancement in the field of nonlinear optics, designed to optimize the performance of traditional LiNbO3 crystals. One of the principal challenges with standard LiNbO3 is its vulnerability to photorefractive damage, which is an optically induced change in the refractive index, typically occurring under exposure to blue or green continuous-wave light. Historically, to counteract this issue, LiNbO3 crystals were maintained at elevated temperatures of 400K or above. However, the introduction of MgO-doping, particularly at concentrations around 5 mol% for congruent LiNbO3, has significantly mitigated this problem.

MgO doping has revolutionized the use of LiNbO3 in various optical applications by dramatically increasing its threshold for laser beam strength, sometimes by as much as 100 times. This enhancement is particularly evident in stoichiometric LiNbO3 crystals doped with just 1 mol% MgO, which have demonstrated a higher photorefractive damage threshold compared to 5 mol% MgO-doped congruent samples. This improvement in damage resistance is complemented by a lower coercive field value, making MgO-doped LiNbO3 an attractive choice for high-performance optical devices.

The physical properties of MgO-doped LiNbO3 are noteworthy, with significant changes observed in transition temperature, activation energy, optical band, optical absorption spectra, and the shift of OH- vibration frequency. These properties reach a threshold composition at just above 5 mole% of MgO concentration, underscoring the importance of precise doping levels to achieve optimal performance. Furthermore, the density and electric activation energy of MgO:LiNbO3 have been extensively studied, reinforcing its suitability for advanced optical applications.