Electro-optic glass for light modulators

•PbO-Bi2O3-Ga2O3 glasses with Ag2O + Sb2O3 are suitable for electro-optic modulators.•The addition of Ag2O/Sb2O3 increases the thermal stability of the glass system.•The investigated glasses are transparent up to 75% from 550 nm to 7.4 μm.•The maximum refraction index value (at 473 nm) is 2.487.•Their electro-optic coefficient falls into the range of 7.47–7.77 × 1012 m × V−2.