Growth and Optical Spectra of Zn:Er:LiNbO3 Crystals Using Bridgman Method

The growth of LiNbO3 single crystal with Er3+ and Zn2+ co-doped using Bridgman method and its characteristic absorption spectra and fluorescence spectra were reported. Large-size crystals initially containing Zn2+ (3%) and Er3+ (0.6%) with good optical quality were obtained using optimized conditions such as a growth rate of 0.8 ∼ 1.5 mm·h−1 and a temperature gradient of about 30 ∼ 35 °C · cm−1 across the solid-liquid interface and the sealed platinum crucible. X-ray diffraction and differential thermal analysis (DTA) were used to characterize the crystals. The results indicate that the concentration of Er3+ ions in crystals, their absorption intensity, and their fluorescence intensity decrease from the bottom to the top in the crystals. However, for the upper part of the crystal, the up-conversion fluorescence intensity is higher than that of the lower part excited by an 800 or 970 nm pump. The effects of the crystal lattice, their structural defect and their effective segregation of Er3+ ions were discussed with respect to the variations of the up-conversion fluorescence intensity.