The Judd-Ofelt parameters are useful for calculation of Stimulated emission cross sections. The values of emission cross sections are comparable with those shown by glasses used in solid state laser applications. This theory gives three intensity parameters ï2, ï4 and ï6, which are related to the local structure in the vicinity of rare-earth ions, and / or the covalency of the rare-earth ion sites. The comparison of calculated with measured lifetimes gives information about non-radiative decay rates. In the absence of nonradiative decay processes, it is not possible to assess the agreement between the Judd-Ofelt theory and the experimental results.