Photoluminescence of Eu³⁺-, Tb³⁺-, Dy³⁺- and Tm³⁺-doped transparent GeO₂-TiO₂-K ₂O glass ceramics

In this paper, we present the photoluminescence properties of Eu ³⁺-, Tb³⁺-, Dy³⁺- and Tm³⁺-doped potassium-titanium-germanate glasses and glass ceramics. Following the x-ray diffraction measurement, the glass structure was established. Compared to Eu³⁺-, Tb³⁺-, Dy³⁺- and Tm³⁺-doped glasses, their respective glass ceramics show stronger emissions due to the presence of the K₂TiGe₃O₉ crystalline phase. For Eu³⁺-doped glass and glass ceramics, five emission bands centered at 578 nm , 592 nm , 614 nm , 653 nm and 702 nm have been observed with 394 nm excitation wavelength. Of them, 614 nm has shown a bright reddish-orange emission. For Tb³⁺-doped glass and glass ceramic, four emission bands centered at 490 nm , 549 nm , 586 nm and 621 nm have been observed with an excitation at 378 nm wavelength. Of them, 549 nm has shown a bright green emission. With regard to Dy³⁺:glass and glass ceramic, a blue emission band centered at 485 nm and a bright fluorescent yellow emission at 576 nm have been observed, apart from (665 nm) emission transition with an excitation at 387 nm , ⁴F_7/2) wavelength. Emission bands of (650 nm) and (700 nm) transitions for the Tm³⁺:glass and glass ceramic, with excitation at (468 nm), have been observed. The stimulated emission cross sections of all the emission bands of Eu³⁺, Tb ³⁺, Dy³⁺ and Tm³⁺:glasses and glass ceramics have been computed based on their measured Δλ (FWHM) and lifetimes (τ_m).