Measurements of the absolute quantum efficiency of neodymium luminescence in high-concentration glasses coactivated with chromium

Direct measurements were made of the absolute quantum efficiency of the luminescence from the ⁴F_3/2 upper active level of neodymium in high-concentration Li–La_1–x–yNd_xCr_y phosphate glass excited at various absorption bands of neodymium and chromium. The quantum efficiency of the chromium luminescence was also determined by the integrating sphere method. The results showed good agreement with measurements of the excitation spectra and decay kinetics of the upper active level of neodymium. Efficient nonradiative energy transfer was observed from the chromium ions to neodymium levels situated above the metastable state. For x=0.3 and y>0.03, nonradiative energy transfer was also observed from the metastable state of neodymium to the chromium ions. It was found that for x=0.3 and y=0.03, when the Nd→Cr reverse transfer was still negligible, approximately 50% of the excited chromium ions transferred their energy to the metastable state of the neodymium ions at room temperature although the luminescence quantum efficiency of chromium was a few percent.