Comparative studies of spectroscopic properties in Er³⁺-Yb³⁺ codoped phosphate glasses

A spectroscopic investigation of an extensive series of commercially available Er³⁺-Yb³⁺ codoped phosphate glasses (IOG-1) with different Er-Yb concentrations have been presented based upon spectroscopic measurements and Judd-Ofelt theory. The composition and the atomic concentration of the respective elements of the glass samples were analyzed. Various spectroscopic parameters were obtained to evaluate the performances of these glasses as a laser material in the eye-safe laser wavelength of 1.53 μm. Using the measured fluorescence lifetimes the radiative quantum efficiency of the ⁴I_13/2 → ⁴I_15/2 transition is estimated to be ∼100% for the glass substrates with an Er³⁺ concentration of lower than 2.0 × 10²⁰ ions/cm³. The stimulated emission and absorption cross-sections were also determined and compared. The infrared and upconversion fluorescence were studied, and under 975 nm excitation the dominant upconversion mechanisms are excited state absorption (ESA) and energy transfer (ET) for the green emission, and ET for the red emission. The data obtained here provide useful guidelines on the choice of IOG-1 glasses with the fixed Er-Yb concentrations.