Mid-Infrared Emission from Sensitized Pr$^{3+}$ in the Low Phonon-Energy Host KPb$_{2}$Cl$_{5}$

Energy transfer from Yb$^{3+}$ to Pr$^{3+}$ was explored in the low-phonon energy host KPb$_{2}$Cl$_{5 }$for 4-5 $\mu $m solid-state laser development. The incorporation of two rare-earth (RE) ions in a low-phonon energy host is expected to increase critical laser parameters such as pump efficiency and emission intensity through energy transfer. Moreover, incorporating the RE ions in a low phonon-energy host is expected to reduce the detrimental effects of non-radiative decay through multi-phonon emission. Evidence of efficient energy transfer was observed in Yb$^{3+} \rightarrow $Pr$^{3+}$ under 980 nm laser excitation This was accomplished by exciting the $^{3}$H$_{4}\rightarrow ^{1}$G$_{4}$ absorption transition of Pr$^{3+}$ at 980 nm in singly doped Pr: KPb$_{2}$Cl$_{5}$ and the $^{2}$F$_{7/2}$ $\rightarrow ^{2}$F$_{9/2}$ absorption transition of Yb$^{3+}$ at the same excitation wavelength in the Pr, Yb: KPb$_{2}$Cl$_{5}$ sample. The integrated emission intensity of Pr$^{3+}$ in the co-doped sample is nearly 11 times larger relative to Pr$^{3+}$ in the singly doped sample. This suggests that energy transfer between Yb and Pr was successful.