Special pure germanium-rich Ga-Ge-As-Se glasses for active mid-IR fiber optics

Highlights: • Special pure Ga_xGe₂₅As₁₅Se_60-x (x = 0; 1; 2; 3; 4; 5) glasses were prepared and investigated. • The glasses have high glass transition temperature (>320 °C) and low tendency to crystallization. • The microstructure, the transmission region and the linear refractive index of glasses were studied. • Dispersion optical parameters of glasses were calculated using the Wemple-DiDomenico model. • For the first time, a single-index Ga₃Ge₂₅As₁₅Se₅₇ glass fiber was fabricated and investigated. - Abstract: Special pure Ga_xGe₂₅As₁₅Se_60-x (x = 0; 1; 2; 3; 4; 5) glasses were prepared using various methods for purification of the glass-forming melt. The glasses are characterized by high transparency in the spectral range 0.8–15 μm, low impurity content, high glass transition temperature (>320 °C), and low tendency to crystallization. The microstructure, the transmission range edges, the optical band-gap energy, and the linear refractive index of the glasses are studied. The refractive index of Ga_xGe₂₅As₁₅Se_60-x (x = 0÷5) glasses measured by ellipsometry increases with the substitution of selenium by gallium. It is for the first time that a single-index Ga₃Ge₂₅As₁₅Se₅₇ glass fiber was fabricated, its minimum optical loss was about 0.6 dB/m at a wavelength of 6.7 μm. High-purity germanium-rich Ga-Ge-As-Se glasses were shown to be a promising material for active mid-IR fiber optics.