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

Abstract Special pure GaxGe25As15Se60-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 GaxGe25As15Se60-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.