Near-infrared luminescence in titanate-germanate glasses co-doped with Cr3+/Ln3+ (Ln=Tm or Ho)

Near-infrared luminescence in titanate-germanate glasses co-doped with Cr³⁺/Ln³⁺ (where Ln = Tm or Ho) have been investigated under different excitation wavelengths. Near-infrared emission spectra and their decays were analyzed for glass samples varying with TiO₂ content. Several emission bands in the 950–1570 nm and 1570–2200 nm spectral ranges are observed for glass samples excited directly at 600 nm (Cr³⁺), which correspond to characteristic transitions of Cr³⁺ and Ln³⁺ (Ln = Tm, Ho) ions. It suggests that the energy transfer processes Cr³⁺ → Tm³⁺ and Cr³⁺ → Ho³⁺ occur. It was also confirmed by the excitation spectra measurements. The experimental results indicate that titanate-germanate glasses co-doped with Cr³⁺/Ln³⁺ (Ln = Tm or Ho) are promising for near-infrared luminescence applications.