Effects of temperature on factors relevant to laser operation near 1.6 µm wavelength in resonantly (in-band) pumped CaF2:Er and SrF2:Er crystals: a comparative study

Single crystals of CaF 2 and SrF 2 containing Er 3+ ions with concentrations between 0.01 and 0.6 at% respectively, were grown using the temperature gradient technique (TGT). Absorption spectra related to the 4 I 15/2 → 4 I 13/2 transition of Er 3+ ions were measured at 5 K to investigate the properties of the crystal field splitting of the 4 I 13/2 multiplet, and at several temperatures in the region 80 K – 300 K to determine the effect of temperature on the spectral bands. The 4 I 13/2 → 4 I 15/2 luminescence spectra were recorded within the same temperature range as for absorption measurement. The analysis of absorption and luminescence spectra provides an in-depth knowledge on the effect of temperature on the factors that govern the efficiency of resonant optical pumping near 1.6 µm and the resulting lasing ability of Er 3+ ions imbedded in CaF 2 and SrF 2 hosts.