Creation of the system for the analysis of the optical properties and the structure around rare earth ions in glass

根据晶场理论，研究了稀土离子在氟化物玻璃中的光学性质。(1)利用分子动力学技术制备了含稀土离子的结构模型。根据点电荷近似下的结构模型得到的晶体场参数，估算了4f电子的能级分裂和跃迁速率。用我们的计算方法再现了ZBLAN（ZrF_4基氟化物玻璃）和YABC（AlF_3基氟化物玻璃）中Pr^<3+>、Er^<3+>和Tm^<3+>离子的吸收光谱。(2)考察了4f能级分裂与由结构模型计算的晶场参数之间的关系。根据这种关系，能级可以分为几组。我们发现了一个组，其分裂是由稀土离子周围的短程结构控制的。我们观察到了与该基团有关的发射光谱，并分析了能级的分裂。结果表明，Tm^<3+>离子在YABC玻璃中主要与8个氟离子配位. (3)模拟了Tm：ZBLAN玻璃的光学性质。通过求解速率方程，计算了Tm^<3+>离子在双波长激发下的能级布居，得到了从^3H_6到^3P_2的跃迁几率和跃迁谱形。我们提出了用于放大1470 nm信号的激发波长的新组合。

The optical properties of rare earth ions in fluoride glasses were investigated on the basis of the crystal filed theory.(1) The structural models containing rare earth ions were prepared by using molecular dynamics technique. The energy splitting of 4f electrons and the transition rate between them were estimated from the crystal filed parameters which were obtained from the structural models on the basis of the point charge approximation. The observed absorption spectra of Pr^<3+>, Er^<3+> and Tm^<3+> ions in the fluoride glasses, such as ZBLAN (ZrF_4 based fluoride glass) and YABC (AlF_3 based fluoride glass), were reproduced by our calculation method.(2) The relation between the splitting of 4f energy level and the crystal filed parameters calculated from the structure models was examined. According to this relation, the energy levels could be classified into several groups. We found one group whose splitting was dominated by the short-range structure around the rare earth ion. We observed emission spectra related to the group and analyzed the splitting of the energy level. It was found that the Tm^<3+> ion was mainly coordinated by 8 fluorine ions in YABC glass.(3) The optical properties of Tm : ZBLAN glass was simulated. The population of the energy levels of the Tm^<3+> ion under dual-wavelength excitation for amplification was evaluated by solving the rate equation with the simulated transition probabilities and spectral shapes of the transitions of which the initial levels were from the ^3H_6 to ^3P_2 levels. We proposed new combinations of the excitation wavelengths for the amplification of the 1470 nm signal.