Effect of iodine on physicochemical and optical properties of Ge20Te77-Se3I (x = 0–10) glasses

Thermodynamic modeling of the Ge-Te-I system is carried out. The dependences of the equilibrium concentrations of components in the condensed and vapor phases on temperature and iodine content are established. The compositional effect on the properties of Ge ₂₀Te _{77- x}Se ₃I _x ( x = 0–10) and Ge ₂₀Te _{72- y}Se _yI ₈ ( y = 1, 3, 5) glasses is studied. In the glasses, with an increase in the iodine content, the glass transition temperature decreases, the stability against crystallization increases, and the short-wavelength transparency edge shifts towards shorter wavelengths. Selenium increases the stability of glasses against crystallization and limits transparency in the long-wavelength spectral range. The Ge ₂₀Te ₆₉Se ₃I ₈, Ge ₂₀Te ₆₇Se ₅I ₈, and Ge ₂₀Te ₆₇Se ₃I ₁₀ compositions are potentially suitable for fabricating optical fibers. The Ge ₂₀Te ₆₉Se ₃I ₈ glass sample with an oxygen impurity content chemically bonded with germanium of less than 50 ppb(wt) and low absorption in the 3–18 μm spectral range is prepared.