Mid-infrared Emission and Energy Transfer Properties of Sensitized Rare Earth Ions in KPb$_{2}$Cl$_{5}$

Mid-infrared emission (4-5 $\mu $m) originating from the first excited state of Pr$^{3+}$ and from the first excited state of Nd$^{3+}$ were generated by means of Yb$^{3+}$ and Tm$^{3+}$ sensitization, respectively. The mechanisms involved in sensitizing Pr$^{3+}$ and Nd$^{3+ }$ions were determined by studying the decay kinetics of the $^{2}$F$_{5/2}\to ^{2}$F$_{7/2}$ transition of Yb$^{3+}$ and the $^{3}$F$_{4}\to ^{3}$H$_{6}$ transition of Tm$^{3+}$ under 970 nm and 1750 nm laser excitation, respectively. It was observed that the emission lifetime of the $^{2}$F$_{5/2}\to ^{2}$F$_{7/2}$ transition and the $^{3}$F$_{4}\to ^{3}$H$_{6}$ transition were reduced considerably in the presence of the activator ions Pr$^{3+}$ and Nd$^{3+}$, respectively. Strong 4-5 $\mu $m emission from Pr$^{3+}$ and Nd$^{3+ }$were observed in Yb, Pr: KPb$_{2}$Cl$_{5 }$and Tm, Nd:KPb$_{2}$Cl$_{5}$, respectively. These findings indicate that significant energy transfer was transpired. Concentration dependent studies will be conducted to ascertain the dopant concentrations for efficient MIR emission.