Spectroscopic investigation of Nd3+ single doped and Eu3+/Nd3+ co-doped phosphate glass for solar pumped lasers

Abstract We report on the fabrication and characterization of Nd 3 + doped phosphate glass to be used as active laser medium for developing solar pumped fiber laser emitting at 1.06 μm. Several Nd 3 + -doped phosphate glass samples were fabricated, with a host composition of (mol%) 65P 2 O 5 :17Li 2 O:3Al 2 O 3 :4B 2 O 3 :5BaO:6La 2 O 3 and with a concentration of Nd 3 + up to 10 mol%. In order to exploit the unabsorbed solar energy by Nd 3 + ions, Eu 3 + co-doping of Nd 3 + -doped phosphate glasses was also investigated to asses a potential increase in the overall pump power conversion efficiency. Physical and thermal properties of single doped and co-doped samples were measured and their spectroscopic properties are discussed. The effect of Nd 3 + doping concentration on emission spectra and lifetimes was investigated in single doped samples in order to study the concentration quenching effect on luminescence performance. The shape of the fluorescence spectrum did not change by increasing the Nd 3 + doping level while the lifetime of the Nd 3 + : 4 F 3/2 was found to decrease. The following characteristic value parameters were calculated: radiative lifetime τ 0 = 367 μs and quenching concentration N 0 = 8.47 E + 20 ions/cm 3 . The Eu 3 + co-doping was found to give a limited increase to the glass pump power absorption limited to the UV range. Although energy transfer from Eu 3 + to Nd 3 + occured, a large Eu 3 + concentration dependent quenching of Nd 3 + fluorescence was observed. This latter process decreases the radiative quantum efficiency of Nd 3 + : 4 F 3/2 emitting level and hence limits the attractiveness of Eu 3 + sensitization for Nd 3 + laser action.