Mid-infrared spectroscopic characterization of Pr3+:Lu2O3

We report spectroscopic characterization of Pr3+:Lu2O3 in the MIR region from 1 to 10 mu m. Lu2O3 possesses good the properties, has relatively low phonon energies, and can be grown in good quality. Moreover, Pr3+ ions possess several low-energy levels that in principle, can give rise to mid-infrared emission. For these reasons, we investigated this material as a potential mid-infrared emitter. From absorption measurements, we identified absorption from the first five multiplets. Moreover, low temperature measurements allowed us to extract the Stark sublevel positions of all these five multiplets and we revised the classical Dieke diagram for Pr3+ in this compound. We also observed near- and mid-infrared emission bands under diode laser pumping. The pump power dependence of the corresponding emission intensities proved the main energy transfer mechanisms that populate the lower lying levels to be cross-relaxation processes and permitted us to discern among the various possibilities and assign the different emission bands to specific transitions. In particular, we observed for the first time MIR emission at 4.4 and 7 mu m in this compound, that is, in the latter case, an emission energy equal to less than three phonons in this crystal host.