Spectroscopic analysis and laser modeling of neodymium-doped potassium lead chloride

We present a discussion of the low-phonon energy host material potassium lead chloride, KPb2Cl5, doped with neodymium. Crystal growth, spectroscopic measurements, and an analysis of the magnetic and electric dipole transitions based on the Judd–Ofelt model are presented. Concentration quenching of the fluorescence is also examined. Based on the spectroscopic data and the known resonances in energy spacing of the first three excited states in neodymium, we suggest the possibility of a 3-for-1 cross-relaxation process. This process may efficiently populate the first excited state, 4I11/2, which we show to be metastable with lifetime on the order of a few milliseconds. Population inversion of this level should be possible enabling a laser based on the 5.5-μm, 4I11/2 to 4I9/2 transition.