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Glass compositions in the gallium-rich region of the ternary GaO3/2–GeO2–NaO1/2vitreous system are studied as a function of the Na/Ga cationic ratio (ranging from 1.30 to 1.61) for a fixed GeO2content. Glass structures are investigated by 71Ga magic angle spinning nuclear magnetic resonance, infrared, and Raman spectroscopies, and the thermal, optical, and physical properties are characterized. Vibrational spectra are interpreted with the help of density functional theory calculations. Gallium oxide generally enters the germania network in fourfold coordination, however, for a Na/Ga ratio below unity, gallium cations tend to charge balance with the formation of five- or six-fold coordination units. When the amount of sodium is greater than gallium, nonbridging oxygens are formed preferably on germanate tetrahedral units. These structural descriptions are used to understand the evolution of glass properties such as glass transition temperature, density, and refractive index.

Rare earth ion doped materials are means to obtain cost-effective infrared light sources, with enough brilliance for applications such as gas sensing. Within a sulfide matrix, the simultaneous luminescence of both Pr^3+ and Dy^3+ in the Ga_5Ge_20Sb_10S_65 glass is reported. The use of these two rare earths is giving rise to a broad continuous luminescence in the 2.2–5.5 µm wavelength range, which could be used as a mid-infrared light source for gas-sensing applications. The demonstration of CO_2 and CH_4 detection using a fiber drawn from these materials is reported.