Spectroscopic properties of Yb2+ in aluminosilicate glass

In contrast to Yb³⁺ which is a well-investigated optically active ion, the spectroscopic properties of its divalent counterpart Yb²⁺ in glasses are hardly investigated, although Yb²⁺ might have a notable influence on the luminescence properties of Yb³⁺-doped glasses even at low Yb²⁺ concentrations because of its strong f-d transitions. In this paper, we report on the preparation and spectroscopic properties of Yb²⁺-doped aluminosilicate glasses that were produced using the normal melt-quench technique. The glass composition is 20CaO·20Al₂O₃·60SiO₂ (mol%). To achieve a sufficient amount of Yb²⁺ in the samples, different methods were applied to influence the red-ox equilibrium during glass melting: firstly, under argon atmosphere and additional argon bubbling, and secondly by the addition of metallic aluminum powder to the batch. The strongly reduced samples show a greenish to brownish yellow coloring which could be attributed to the strong absorption of Yb²⁺ ions in the UV to blue spectral range. The absolute Yb²⁺ concentration in the glass and the molar extinction coefficient of Yb²⁺ was obtained by spectroscopic measurements. If irradiated with UV light, the Yb²⁺-doped samples show a broad fluorescence emission in the wavelength range from 450 to 700 nm with a peak at around 515 nm.