Nd³⁺ Cluster Adjustment in Nd³⁺:CaNb₂O₆ by Codoping La³⁺ Buffers for Improvement of Fundamental and Self-Stimulated Raman Scattering Laser Operation: A Study Case from the Perspective of Defect Chemistry

The fluorescence quenching caused by Nd3+ clusters in Nd3+-doped crystals even at low Nd3+ concentration has restrained the performance of Nd3+ lasers. In this work, Nd3+:CaNb2O6 and Nd3+:La3+:CaNb2O6 single crystals have been grown by the Czochralski method. RE3+ (RE3+ = Nd3+, La3+) ion incorporation mechanisms, the formation of Nd3+ clusters, and the feasibility of La3+ ions as buffers in RE3+:CaNb2O6 crystals have been demonstrated and assessed by atomistic simulation methods. The spectral and laser properties of Nd3+:CaNb2O6 and Nd3+:La3+:CaNb2O6 have been measured. All of the results indicate the Nd3+ dimers with distances between Nd3+ close to the critical interaction distance have formed in Nd3+:CaNb2O6 and the La3+ ions as buffers can alleviate the interaction of Nd3+ effectively in the Nd3+:La3+:CaNb2O6 as expected. Benefiting from the introduction of La3+ buffers, about 2.6 W fundamental laser with a slope efficiency of 36.5% and about a 310 mW self-stimulated Raman scattering laser with conversion and slope efficiencies of 8.3% and 9.5%, respectively, which are superior to those of Nd3+:CaNb2O6, have been achieved in Nd3+:La3+:CaNb2O6.