SPECTROSCOPIC AND LASER PROPERTIES OF PM-3+

Some of the spectroscopic properties of the promethium ion (Pm**3** plus ) were investigated in order to assess its feasibility for laser action. The fluorescence spectra and decays from the **5F//1//,//2 manifolds were measured in 11 dielectric materials. The calculated peak emission cross sections are comparable to those for Nd**3** plus in the same hosts. For one host, a lead-indium phosphate glass, application of the Judd-Ofelt theory yielded values of radiative rates, branching ratios, and emission cross sections from the **5Fm//1 manifold. Laser action at 933 and 1098 nm was observed due to the **5F//1 yields **5I//5 and **5F//1 yields **5I//6 transitions, respectively. The calculated thresholds for laser action were in good agreement with experiment. It is concluded that Pm lasers will perform as well as Nd lasers, but with laser operation blue-shifted to the 920-nm region.