Effects of CaO/Al2O3 ratio on structure and spectroscopic properties of Nd3 +-doped CaO-Al2O3-BaO aluminate glass

Nd3+-doped CaO-Al2O3-BaO glasses with varying CaO/Al2O3 ratios were synthesized, and their thermal, structural, absorption, and emission properties were characterized as functions of the CaO/Al2O3 ratio. The thermal stability of the glasses was analyzed by differential scanning calorimetry. The Raman spectra indicated that the amount of AlOAl bridging oxygen bonds decreased and the amount of the Alnon-bridging oxygen (NBO) bonds increased with an increase of the CaO/Al2O3 ratio. A broadband emission was observed in the fluorescence spectra, and the full width at half maximum bandwidth was found to increase from 38.6nm to 41.2nm with the increase of CaO/Al2O3 ratio. Meanwhile, the fluorescence peak shifted from 1064nm to 1068nm. Based on the Judd–Ofelt parameters, the transition probabilities, emission cross-sections and gain parameters of the glasses were calculated to evaluate the optical amplification performances; the stimulated emission cross-section decreased from 2.11×10−20 to 1.35×10−20cm2 with the increase in the CaO/Al2O3 ratio. These results indicate that Nd3+-doped CaO-Al2O3-BaO aluminate glasses with a broadband fluorescence bandwidth and suitable gain property have potential for the application in high-energy ultrashort-pulse lasers.