Rare earth–aluminum oxide glasses for optical applications

Glasses based on rare earth oxides and aluminum oxide with 0–20 mol% SiO2 provide a combination of optical properties, mechanical and chemical stability, and process characteristics not available in other oxide materials. Properties of the glasses include: refractive index 1.7–1.8, low dispersion (Abbe number ∼40), high solubility of optically active dopants, homogeneous chemical composition, long fluorescence lifetimes at dopant concentrations up to 5 mol%, broad fluorescence bandwidth, and infrared transmission to ≈5000 nm. The glasses are hard, strong and resist chemical attack and they can be cast in sections 5–10 mm thick. This paper briefly describes glass processing and presents bulk glass properties including results of experiments to study infrared fluorescence at wavelengths ∼1550, ∼2900 and ∼1030 nm from Er- and Yb-doped glasses that were optically pumped at 980 nm.