Characteristics of upconversion luminescence of CaF$_{2}$ : Er powders upon laser excitation at 1.5 $\mu$m

The characteristics of upconversion luminescence of CaF$_{2}$ : Er crystalline powders were investigated upon excitation of Er$^{3+}$ ions to the $^{4}I_{13/2}$ level by laser radiation at 1531.8 nm. The energy yield values of upconversion luminescence were determined for the spectral ranges 380–780 and 380–1100 nm. It was found that upconversion luminescence of CaF$_2$:Er powders with concentrations of 0.5, 2, 4, 6, 8, 10, 11, 13, 15, and 17% of Er$^{3+}$ ions is characterized by correlated color temperatures of about 5100, 2142, 1726, 1738, 1773, 1757, 1762, 1765, 1735, and 1714 K, respectively.