Enhancement of the structure, optical, and spectroscopic properties of fluoroborosilicate glass doped with thulium

Glass composition of (0.15-x)LiF–0.15NaF–0.01Al2O3–0.24SiO2–0.45B2O3–xTm2O3, in which x varies from 0.01 to 0.08, has been prepared by melt-annealing technique. The glass density values increased as thulium content increases from 2.359 to 2.735 g/cm3. The structure of glass showed the presence of trigonal BO3, O2B–F, tetrahedral BO4, O3B–F units, Si–O–Si, B–O–Si, and B–O–B linkages. The optical properties of the prepared glass were investigated. The optical absorption spectra revealed four characteristic bands in the ultraviolet and near-infrared regions for thulium ions. Judd–Ofelt parameters such as Ω2, Ω4, and Ω6 were calculated and took the order of Ω2 > Ω6 > Ω4. The radiative transition probability, branching ratio, and radiative lifetime were deduced from the Judd–Ofelt parameters. Moreover, the optical transition, refractive index, and phonon energy were calculated to show the effect of thulium content on borosilicate glass.