Improvements on the optical properties of Ge–Sb–Se chalcogenide glasses with iodine incorporation

• A series of Ge–Sb–Se–I chalcohalide glasses were prepared and some key properties were investigated systematically, especially of the mechanisms of the halogen I affecting.
• The mid-IR transparency of conventional Ge–Sb–Se chalcogenide glasses was improved with iodine incorporation.
• The structural evolutions of Ge–Sb–Se–I glasses were revealed by Raman spectroscopy and the intensity of weak absorption tail was decreased by decreasing glass network defects.

Decreasing glass network defects and improving optical transmittance are essential work for material researchers. We studied the function of halogen iodine (I) acting as a glass network modifier in Ge–Sb–Se-based chalcogenide glass system. A systematic series of Ge20Sb5Se75−xIx (x = 0, 5, 10, 15, 20 at.%) infrared (IR) chalcohalide glasses were investigated to decrease the weak absorption tail (WAT) and improve the mid-IR transparency. The mechanisms of the halogen I affecting the physical, thermal, and optical properties of Se-based chalcogenide glasses were reported. The structural evolutions of these glasses were also revealed by Raman spectroscopy and camera imaging. The progressive substitution of I for Se increased the optical bandgap. The WAT and scatting loss significantly decreased corresponding to the progressive decrease in structural defects caused by dangling bands and structure defects in the original Ge20Sb5Se75 glass. The achieved maximum IR transparency of Ge–Sb–Se–I glasses can reach up to 80% with an effective transmission window between 0.94 μm and 17 μm, whereas the absorption coefficient decreased to 0.029 cm−1 at 10.16 μm. Thus, these materials are promising candidates for developing low-loss IR fibers.