Thermal, Optical, and IR-Emission Properties of Extremely Low Hydroxyl TeO₂-WO₃-Bi₂O₃-La₂O₃-xEr₂O₃ Glasses for Mid-Infrared Photonics

Abstract

A series of glass samples of the tungsten–tellurite system TeO2-WO3-Bi2O3-(4-x) La2O3-xEr2O3, x = 0; 0.4; 0.5; 0.7; 1.2; 2; 4 mol%, CEr = 0 - 15 × 1020 cm−3 were synthesized from high-purity oxides in an oxygen flow inside a specialized sealed reactor. In all samples of the series, an extremely low content of hydroxyl groups was achieved (~n × 1016 cm−3, more than 4 orders of magnitude lower than the concentration of erbium ions), which guarantees minimal effects on the luminescence properties of Er3+. The glasses are resistant to crystallization up to 4 mol% Er2O3, and the glass transition temperatures do not depend on the concentration of erbium oxide when introduced by replacing lanthanum oxide. Thin 0.2 mm plates have high transmittance at a level of 20% in the 4.7–5.3 µm range, and the absorption bands of hydroxyl groups at about 2.3, 3, and 4.4 µm, which are typical for ordinary tellurite glass samples, are indistinguishable. The introduction of erbium oxide led to an insignificant change in the refractive index. Er2O3-concentration dependences of the luminescence intensities and lifetimes near the wavelengths of 1.53 and 2.75 μm were found for the 4I13/2–4I15/2 and 4I11/2–4I13/2 /transitions of the Er3+ ion. The data obtained are necessary for the development of mid-infrared photonics; in particular, for the design of Er3+-doped fiber lasers.

Keywords

• high-purity tellurite glass
• Er₂O₃ content
• hydroxyl groups
• crystallization
• glass transition temperature
• luminescence