Spectroscopic Properties of Yb~(3+) in Phosphate Glass

测量了不同温度下Yb~(3+)离子在磷酸盐玻璃中的吸收光谱，发现吸收峰随温度升高发生蓝移，且有一反常吸收峰出现，可能来自另一种格位中心。根据低温下的吸收光谱和荧光光谱确定了Yb~(3+)离子在磷酸盐玻璃中的能级结构，并利用选择激发荧光光谱研究了掺Yb~(3+)磷酸盐的格位选择特征。Recently, Yb~(3+) doped solid-state materials are attractively used as gain media of high efficiency, high power laser with the development of InGaAs laser diode. Yb~(3+) doped laser glass enable diode pumping without temperature stabilization because it has larger inhomogeneous width of the absorption lines. Due to broad emission lines around 1.02mum, Yb~(3+) doped glass also is a good candidate as a pump source for Pr~(3+) doped laser fiber, which has potential application as amplifiers in the 1.3mum communication window. Determination of energy levels and other spectroscopic parameters of interest for Yb~(3+) laser action in glass is difficult because the inhomogeneous broadening of optical spectra is comparable to the Starke splitting, and hence masked the structure. However, a study of the energetic parameters of lasers and amplifiers require knowledge of the ratio between the homogeneous and inhomogeneous width of transitions. In this paper the absorption spectra of Yb~(3+) doped phosphate glass were measured at different temperatures and the blueshift of the absorption peaks was discovered. There was abnormal absorption line in absorption spectra at low temperatures, which arised possible from another group of sites occupied by small partial Yb~(3+) ions. Due to the addition of B_2O_3, Al_2O_3 and Nb_2O_3, [BO_4], [BO_3], [AlO_4] and [NbO_6] partially take the place of PO_4 tetrahedral as network formers. The [PO_4-Yb, [AlO_4]-Yb, [BO_3]-Yb and [NbO_6]-Yb bond distances must be different and cause the great break of the symmetry of the coordination sphere of oxygens around Yb~(3+) ions. When a[YbO_6] coordination sphere is surrounded by such network formers which possess different cationic field strengths, polarizabilities and coordination numbers of oxygen, the characteristic of Yb-O bond are varied and the local structures in the vicinity of the emitting ions may be distorted strongly, which result that a small portion of ytterbium ions reside in another type sites different from those occupied by the ytterbium ions which give rise to the principal spectra. The energy levels of Yb~(3+) ion in phosphate glass were obtained according to the absorption and emission spectra at low temperature. The sites selective fluorescence spectra had been investigated at low temperature, too