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 Er³⁺ 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 ⁴I_13/2→⁴I_15/2 transition of Er³⁺. In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the ⁴I_13/2 emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of 0.73×10^-20 cm², 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 ⁴I_13/2→⁴I_15/2 emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb³⁺ ions in heavily doped CaF₂ erbium ions in the CaF₂-CeF₃ crystal reside in numerous sites with dissimilar relaxation rates.