Upconversion Studies of Er3+ Doped into Low Phonon-Energy Hosts KPb2Cl5 and KPB2Cl5 via 0.97 $\mu$m and 1.5 $\mu$m Laser Excitation

A comparative study of the wavelength dependence of the Er3+ upconversion in low phonon-energy hosts KPb2Cl5 and KPb2 Br5 will be presented. Initial measurements indicate that visible and infrared upconversion was generated under 0.97 $\mu$m and 1.5 $\mu$m laser excitation. Using time resolved emission, spectral emission, and spectral absorption data the dominant upconversion mechanisms involving excited state absorption and/or energy transfer were investigated. In addition, special emphasis was geared toward a comparative study of the detrimental effects of upconversion under resonant pumping conditions (1.5 $\mu$m) for possible applications in the eye-safe wavelengths (1.5 -- 1.6 $\mu$m) region.