Optical properties of Ho3+-doped novel oxyfluoride glasses

Novel oxyfluoride glasses SiO2-Al2O3-Na2O-ZnF2 doped with Ho3+ and Ho3+/Yb3+ were fabricated. The optical properties of the synthesized glasses were experimentally and theoretically investigated in detail. The experimental and calculated oscillator strengths of Ho3+ were determined by measurement of absorption spectrum of Ho3+-singly doped glass. According to the Judd-Ofelt theory, the Judd-Ofelt parameters were calculated, by which the radiative transition probabilities, fluorescence branching ratios and radiative lifetimes were obtained. Visible upconversion luminescence was observed under 980 nm diode laser excitation and the influence of Yb3+ concentration on the emission bands were also investigated. The dependence of the upconversion emission intensity upon the excitation power was examined, and the upconversion mechanisms were discussed.