Effect of bismuth oxide on the thermal stability and Judd–Ofelt parameters of Er 3+/Yb 3+ co-doped aluminophosphate glasses

Abstract

The Er 3+/Yb 3+ co-doped glasses with compositions of xBi 2O 3–(65 − x)P 2O 5–4Yb 2O 3–11Al 2O 3–5BaO–15Na 2O (where x = 0, 2.5, 5, 7.5 and 10 mol%) were prepared using the normal melt quench technique. The optical absorption spectra of the glasses were recorded in the wavelength range 300–1700 nm. The effect of Bi 2O 3 content on the thermal stability and absorption spectra of glasses was investigated. In addition, the Judd–Ofelt parameters and oscillator strengths were calculated by employing Judd–Ofelt theory. It was observed that the positions of the fundamental absorption edge and cut-off wavelength shifted towards red as the content of Bi 2O 3 increased. However, there were no red shifts found both in the peak wavelength and in the center of mass wavelength of all absorption bands with Bi 2O 3 content increasing. The results of Judd–Ofelt theory analysis showed that Judd–Ofelt parameters Ω t ( t = 2, 4, 6) changed sharply when Bi 2O 3 concentration exceeded 5 mol%. The variation trends of experimental oscillator strength were similar with those of Judd–Ofelt parameters as function of Bi 2O 3 concentrations. Moreover, differential scanning calorimetry experiments showed that the increases of Bi 2O 3 content weakened the network structure and then lowered the thermal stability of the glasses. The spontaneous emission probability A rad, branching ratio β and the radiative lifetime τ rad were also calculated and analyzed. The stimulated emission cross-section of Er 3+ was calculated according to the McCumber theory. It was found that the stimulated emission cross-section of Er 3+ was monotonically increases with Bi 2O 3 content increasing.