Enhancement of far-infrared laser damage threshold in Ge-As-Se glass fiber.

The application of As-Se chalcogenide glasses in high-power laser delivery is hindered by their low damage threshold due to their weak chemical bonds. To solve this, we introduced germanium elements into the As-Se glasses and optimized the composition to raise the glass transition temperature (T_g) and enhance the laser damage threshold (LDT). From the correlation among various parameters including T_g, LDT, and fiber loss, we concluded an optimized composition of Ge₂₃As_13.5Se_63.5/Ge₂₃As_12.5Se_64.5 glass. After effective purification and preform extrusion, the glasses were processed into high-quality step-index fiber (core diameter of 300 µm), which exhibits a minimum loss of 0.9 dB/m at 6.9 µm and is capable of withstanding an input CO₂ laser power of 19.96 W at a wavelength of 10.6 µm, equal to a power density of 28.25 ± 0.02 kW/cm² in air. This is nearly 2.3 times higher than that previously reported for Ge-As-Se fibers. This establishes a material foundation for achieving far-infrared high-energy laser systems using Ge-As-Se fibers in the future.