Yb^3＋,Er^3＋：YAG透明陶瓷的制备和1.5μm波段光谱性能研究

Fabrication of Yb^(3+),Er^(3+):YAG transparent ceramics and study of its 1.5 μm fluorescence spectrum

采用固相法和真空烧结技术制备了5at%Yb3+,2at%Er3+:YAG透明陶瓷.在1760℃真空烧结30h后,陶瓷样品具有较高透过率.SEM观察表明制备的透明陶瓷在晶粒和晶界处无气孔、第二相的存在.样品的吸收光谱和荧光光谱的测试结果表明:Yb3+在940nm波长处有具有较强的吸收系数.样品在1030nm波长的荧光寿命仅为0.274ms,以及在1.5μm波段的荧光衰减寿命曲线中,初始的荧光强度呈上升趋势,这些表明了Yb,Er:YAG陶瓷中的Yb3+→Er3+离子间存在能量转移.利用Judd-Ofelt理论拟合出Er3+的强度参数Ωλ,计算出了各能级跃迁寿命和积分发射截面等参数.Er3+离子在1.5μm波段的光谱参数(发射截面和荧光寿命)的理论结果与实验结果符合较好.比较了Yb,Er:YAG透明陶瓷各能级跃迁的光谱参数,1.5μm波段对应的4I13/2→4I15/2能级跃迁较其他能级跃迁具有较大的发射截面、荧光分支比和上能级寿命,证明了Er,Yb:YAG透明陶瓷实现在1.5μm人眼安全波段激光输出的可行性.

5at%Yb^ 3＋ ,2at%Er^ 3＋ ：YAG transparent ceramics possessing a high transmittance was sintered at 1760℃ for 30 h by solid-state method and vacuum sintering technique. The sample exhibited pore-free structure and had no secondary phase in the grain boundary and in the grain, as observed in the SEM photograph. The sample＇s absorption and fluorescent spectra show that the Yb^ 3＋ ions have a high absorption coefficient at 940 nm. The decay life-time at the 1030 nm wavelength is only 0.274 ms and the initial intensity has an ascending tendency in the fluorescent life-time curve at the wavelength range of 1.5 μm, both of which demonstrate the existence of energy transfer from Er^ 3＋ ions to Yb^ 3＋ ions. The life-time and stimulated emission cross section of electronic transition between some levels were calculated with the intensity parameter Ωλ of Er^ 3＋ acquired from Judd-ofelt theory. The experimental results of the spectrum parameters （the emission cross section and fluorescent life-time）of Er^ 3＋ ions in the wavelength range of 1.5 μm are the same as the results of the Judd-Ofelt theory. The transition between ^4I 13/2 and ^4I 15/2 simultaneously has a large stimulated emission cross section, fluorescence ratio and upper level life-time relative to the other energy level transitions of the sample, which makes the laser output of Er,Yb：YAG transparent ceramics in the wavelength range of 1.5 μm, the eye-safe wavelength range, possible.