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

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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.