Laser characterization of an Er3+/Yb3+ doped phosphate glass near 1.5 µm with varying dopant concentrations

Abstract

We describe the design and construction of a laser setup suitable for the characterization of the lasing performance of Er3+/Yb3+ co-doped bulk phosphate glass lasers operating near 1.5 & micro;m. Phosphate glass samples with a constant thickness of 2 mm and with varying concentrations of erbium and ytterbium were investigated by performing continuous-wave (CW) output power, power slope efficiency, output spectrum, and incident threshold pump power measurements. The variation of these laser parameters was investigated as a function of erbium and ytterbium concentration in order to determine the optimum combination of Er3+/Yb3+ concentration that maximizes the output power and power slope efficiency, and minimizes the lasing threshold pump power. Three different sets of phosphate glass samples were used: 1) set 1 includes phosphate samples with a constant Yb3+ concentration of 8 mol% and varying Er3+ concentration of 0.05, 0.1, 0.15, 0.25, 0.5, 0.75, and 1 mol %, 2) set 2 includes phosphate samples with a constant Er3+ concentration of 0.25 mol% and varying Yb3+ concentration of 2, 4, 6, 8, and 10 mol%, and 3) set 3 includes phosphate samples with a constant Er3+ concentration of 0.5 mol% and varying Yb3+ concentration of 2, 4, 6, 8, and 10 mol%. The optimum combination of concentrations was found as 0.25 mol% Er3+ and 6 mol% Yb3+ for the sample length of 2 mm and output coupler transmission of 0.6%. Laser characterization of this glass resulted in cw output power of as high as 43 mW with 410 mW of pump power and a lasing threshold pump power of 47 mW, giving 12% of slope efficiency with respect to absorbed pump power. The tuning capability of this glass laser was also investigated, and a broad range of tuning was achieved from 1484 to 1582 nm.