Mid-infrared spectroscopy of Praseodymium doped Ternary Lead Halides

Solid-state lasers operating in the mid-infrared (MIR) wavelength (3-5$\mu $m) region are important for applications such as remote sensing of biochemical agents and military countermeasures. Solid-state laser hosts based on oxide and fluoride crystals are limited by non-radiative decay through multi-phonon relaxation. Ternary lead halides have recently become of interest as new hosts for mid-infrared gain media because of their low maximum phonon energies ranging from 140 to 205 cm$^{-1}$. The low-phonon energies allow for efficient rare earth emission at mid-infrared wavelengths. In this paper we report on the optical properties of several Pr$^{3+}$ doped ternary lead halides including KPb$_{2}$Cl$_{5}$, RbPb$_{2}$Cl$_{5, }$KPb$_{2}$Br$_{5}$, and RbPb$_{2}$Br$_{5}$. The crystals were grown using a self-seeded Brigdman technique. Broad MIR emission spectra centered on $\sim $ 4.6 $\mu $m with a band width of $\sim $0.9 $\mu $m were observed upon optical excitation at 1.907 $\mu $m. Room temperature lifetimes varied between 1.5 ms and 5.0 ms depending on the host composition. More details of MIR emission properties and energy level assignments will be presented at the conference.