Intensities and spectral features of the ~4I_(13/2)-~4I_(15/2) potential laser transition of Er^(3+) centers in CaF_2-CeF_3 disordered crystal

A CaF2-CeF3 disordered crystal containing 1.06% of Er^3＋ ions was grown by the temperature gradient technique.Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the ^4I13/2→^4I15/2 transition of Er^3＋. In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the ^4I13/2 emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of 0.73 × 10^-20 cm^2, and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature ^4I13/2→^4I15/2 emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb^3＋ ions in heavily doped CaF2 erbium ions in the CaF2-CeF3 crystal reside in numerous sites with dissimilar relaxation rates.

Thermal and radiative characteristics of oxyfluoride glass singly doped with lanthanide ions

Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y≤15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H’ and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ωt along the lanthanide series was presented and discussed.