Zn∶Er∶LiNbO_3单晶的坩埚下降法生长及光谱特性

Growth and Optical Spectra of Zn∶Er∶LiNbO_3 Crystals by Bridgman Method

报道了Zn:Er:LiNbO3单晶的坩埚下降法生长工艺. 通过控制晶体生长固液界面的温度梯度(30～35 ℃·cm-1)、晶体的生长速度(0.8～1.5 mm·h-1)、密闭Pt坩埚等条件生长了宏观无缺陷的Zn2+(3%)和Er3+(0.6%)共掺的LiNbO3单晶. 用X射线衍射(XRD)和差热分析(DTA)表征了获得的晶体, 并测量了晶体不同部位的吸收光谱和荧光谱. 从吸收光谱以及由XRD数据计算所得的晶胞参数推断, 沿生长方向Er3+在晶体中的浓度分布逐步减少. 光谱数据表明, 晶体底部样品的吸收强度和荧光强度要比顶部大, 而对应于Er3+上能级4S3/2和2H11/2跃迁至基态4I15/2的绿光发射, 晶体底部却比顶部表现出更高的上转换效率. 从晶体的内部结构、缺陷情况以及Er3+的分凝现象解释了产生上述现象的内在机制.

The growth of LiNbO3 single crystal with Er^3＋/Zn^2＋ co-doped by the bridgman method and the characteristics of absorption spectra and fluorescence spectra were reported. By means of the optimized conditions such as growth rate of 0.8- 1.5 mm·h^-1, temperature gradient about 30- 35 ℃·cm^-1 across the solid-liquid interface and sealed platinum, large size crystals containing Zn^2＋ （ 3 % ） and Er^3＋ （0.6%） with good optical quality were obtained. X-ray diffraction and DTA were used to characterize the crystals. The results indicate that the concentration of Er^2＋ ions in crystals decrease along the growth direction, the absorption intensity and the fluorescence intensity of Er^3＋ ions also decrease along the er, for the upper part crystal growth direction. However,for the upper part crystal , the upconversion fluorescence intensity is higher than that of the lower part crystal excited with 800 or 970 nm pump. The effects of crystal lattice, structure defect and effective segregation of Er^3＋ ions were discussed in respect to the variations of upconversion fluorescence intensity.