Preparation and performance of Ho³⁺/Yb³⁺ co-doped fluorosilicate-emitting broadband near-infrared glasses

In this study, Ho³⁺/Yb³⁺ co-doped near-infrared fluorosilicate glass was melting with different concentrations of rare earth ions using a high-temperature melting method. Under 980 nmLD excitation, the Ho³⁺/Yb³⁺ co-doped fluorosilicate glass emits a near-infrared radiation of about 2.0 μm. The upconversion fluorescence spectrum reveals weak green light and strong red light. Next, the energy transfer mechanism and spectral characteristics of near-infrared radiation were examined. Fluorosilicate glass has favorable conditions such as relatively low cost, high light transmittance, and good thermal stability. Ho³⁺ the emission cross-section and gain coefficient were calculated to be 0.51 × 10^–20 cm² and 0.903 cm⁻¹, respectively. Furthermore, given the Judd–Ofelt theory, calculated and analyzed the Ho³⁺/Yb³⁺ co-doped Ω_t (t = 2, 4, 6) of 4.25, 2.45, and 0.8, respectively, indicating that the stimulated emission of Ho³⁺ was strong. The sample’s maximum fluorescence lifetime at 2.0 μm was 0.856 ms, which was 0.182 ms longer than that of silicate glass. This indicates that the addition of fluoride is beneficial to improve the fluorescence lifetime at 2 μm. According to the testing results, Ho³⁺/Yb³⁺ co-doped fluorinated silicate glass has a promising development potential for broadband near-infrared fiber and laser materials.