Defect structures and optical characteristics of Er3+ ion in Er:LiNbO3 crystals

Congruent Er:LiNbO3 crystals were grown by Czochraski method. The OH− absorption and UV–vis-near infrared absorption spectra indicated that Er3+ cluster sites were formed in LiNbO3 crystal doped with 3 mol% Er3+ ions. Studies on the stokes and anti-stokes spectra showed that the formation of Er3+ cluster sites could increase the rate of cross relaxation processes. Judd–Ofelt theory was carried out to discuss the spectral characteristics of Er3+ ions in Er:LiNbO3 crystals. Based on Füchtbauer–Ladenburg and McCumber theory, the emission cross section of the 4I13/2 → 4I15/2 transition of Er3+ ion was calculated, and the potential laser performance was evaluated by the gain cross section spectra. Er:LiNbO3 crystal codoped with Zn2+ ions was also grown to discuss the relation between the defect structure and optical characteristics of Er3+ ion.