Infrared Emission and Upconversion Studies of Er$^{3+}$ Doped in the Low Phonon-Energy Hosts KPb$_{2}$Cl$_{5}$ and KPb$_{2}$Br$_5$*

There continues to be interests in Er$^{3+}$ doped materials that can generate efficient emission in the 1.5-1.6 um range for eye-safe laser applications and optical communications. Directly pumping the $^{4}$I$_{13/2}$ band of Er$^{3+}$ has been extensively studied in many hosts, such as YAG, however, it is well understood that the excitation of Er$^{3+}$ through this channel automatically generates unwanted upconversion emission, which depletes $^{4}$I$_{13/2}$ level of Er$^{3+}$ and moreover produces unwanted heating of the crystal. In this study, cw and pulsed laser excitation of the $^{4}$I$_{13/2}$ band of Er$^{3+}$ will be explored as a function of host material (KPb$_{2}$Cl$_{5}$ and KPb$_{2}$Br$_{5})$ rare-earth ion concentration, and temperature in the search for the optimum combination of variables to minimize upconversion and concurrently generate more efficient 1.5 $\mu$m emission from Er$^{3+}$.