Thulium sensitization of praseodymium mid-infrared transitions in potassium lead chloride laser crystals

Energy transfer is reported from Tm/sup 3+/ to Pr/sup 3+/ in co-doped KPb/sub 2/Cl/sub 5/ laser crystals. Pumping Tm/sup 3+/ with 800 nm laser diodes results in broad emission of mid-infrared fluorescence between 4000 and 5500 nm.