Determination of fluorescence quantum efficiency and laser emission cross sections of neodymium crystals: Application to KNdP4O12

The stimulated emission cross sections σLof neodymium crystals at the laser wavelengths (1.05 and 1.32 μm) are useful parameters to predict their laser performance. The determination of σLhas traditionally been a delicate experimental task. We describe here a method which relies upon the measurement of the branching ratios of the radiative transitions from the⁴F3/2doublet to the⁴I multiplets, and the calibration is provided by an absorption measurement concerning a⁴I9/2→⁴F3/2transition. The precise determination of the spectrometer system response over a broad spectral interval is not required. This method also leads to the value of the fluorescence quantum efficiency η of the⁴F3/2level. It is applied here to potassium-neodymium tetrametaphosphate, KNd P4O12.