Ternary borosilicates as potential cladding glasses for semiconductor core optical fibers

Our study advances the development of new ternary silicate glasses for use as a designed cladding for semiconductor core optical fibers using molten core draw process. In order to fabricate high-quality hybrid fibers (homogeneous core shape, low amount of bubbles, low internal stress, no cracking), oxide glasses are the best choice as cladding materials. These glasses should be engineered with tailored thermal properties (coefficient of thermal expansion (CTE) and drawing temperature) so they match those of the semiconductor. Glasses in the system (50SiO₂-(20 − x)Na₂O-(25 + x)B₂O₃-5MO) with x = 0 and 10 and MO = ZnO, TiO₂, GeO₂, Ga₂O₃, and Al₂O₃ and in the system 50SiO₂-10Na₂O-(40 − y)B₂O₃-yTiO₂ with y = 0, 1.25, 2.5, and 5 were investigated. Their thermal properties were measured and discussed with regard to the glass structure analyzed using FTIR spectroscopy. Due to their rigid network, which leads to beneficial thermal properties including low CTE (~5 ppm K⁻¹), the Ge-containing glass with x = 10 is a promising cladding candidate when preparing a Ge core fiber and the Ga or Zn- containing glasses when preparing an InAs core.