Optical properties of Dy3+ ions in alkali tellurofluorophosphate glasses for laser materials

Optical absorption and emission spectra were performed for Dy3+ ions doped alkali tellurofluorophosphate glasses. The intensity parameters from the measured oscillator strengths were evaluated using the Judd-Ofelt (J-O) theory. The observed and calculated oscillator strengths (f) are found to be in reasonable agreement with one another. The evaluated J-O parameters are used to predict radiative transition probabilities (A(R)), total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)) and branching ratios (beta(R)) for various excited levels of Dy3+ doped alkali tellurofluorophosphate glasses. The predicted tau(R) and beta(R) values of F-4(9/2) transition are compared with the experimentally measured values. The lifetime of the F-4(9/2) level was measured with a quantum efficiency of 80% for Dy3+ : RTFP (R = Li, Na, K) glasses. Stimulated peak emission cross-sections (sigma(e)) for different emission transitions were estimated from emission spectra. From the magnitudes of the stimulated emission cross-sections, branching ratios, multiphonon relaxation rates (W-MP), the most potential laser transitions are identified and the utility of these glasses as laser active materials is discussed. A thermalization process between the F-4(9/2) and I-4(15/2) levels is also reported.