Middle infrared luminescence of rare earth ions in silver halide crystals

Middle infrared lasers for countermeasures against heat seeking missiles are currently under development. These systems, based on diode pumped solid state lasers pumping optical parametric oscillators, are complex, bulky and expensive. Middle infrared fiber lasers in the 3 to 5 μm spectral region which operate without a need for frequency conversion may provide an attractive option. We have investigated the luminescence of silver bromide-chloride crystals and fibers doped with Pr^3- ions in the near and middle infrared spectral ranges. The emission, excitation, and absorption spectra, as well as the kinetic parameters, were measured over a broad temperature range. The crystal activation was produced by growing from the melt. No differences were found between the luminescence properties in the crystals and the fibers. The Judd-Ofelt analysis was applied to the Pr doped crystals, and the transition rates, branching ratios, and the quantum efficiencies were calculated. Good agreement was obtained between the theory and the experiment, The strong middle infrared luminescence and the kinetic parameters of these crystals make them good candidates for the fabrication of fiber lasers in 4 -5.5μm spectral range. Such lasers would be very useful for countermeasure devices.