Emission cross section and fluorescence efficiency of Nd-pentaphosphate

The room-temperature cross sections for the Nd³⁺⁴ levels to the⁴ and⁴ manifolds (lower laser state and ground state, respectively) in NdP5O14are measured by two spectroscopic methods. A value for the largest cross section of cm²is found. The highest effective cross section, resulting from superposition of two lines at 1.051 μm, gives a laser gain per Nd ion which is about 2/3 of the maximum gain in YAG:Nd. The relative branching ratio into the⁴ and⁴ manifolds is 0.65:0.35. Comparison of the integrated cross sections with the measured lifetime for 1-percent Nd in LaP5O14indicates a combined efficiency <0.1 for the remaining transitions, namely radiative decay into the⁴ and⁴ manifolds and multiphonon quenching. A measurement of temperature dependence of fluorescence lifetime supports this last result.