CO2 laser annealing of Ge core fibers with different core diameters

Abstract The Ge core fibers with 20-μm, 44-μm, and 62-μm core diameters were annealed by CO2 laser, respectively. The effect of different core diameters on the Ge core fiber in CO2 laser annealing was mainly investigated. Raman frequency maps show that the larger diameter core fiber required higher laser power annealing to effectively eliminate residual stresses in the core. The COMSOL Multiphysics was used to simulate the temperature change of Ge core with different diameters during the CO2 laser annealing process. The simulation results show that the temperature of the small Ge core is higher than that of the large Ge core at the same laser power. The SiO2 cladding do not introduce significant residual stresses into Ge core during the fiber drawing process. The propagation losses were measured using a quantum cascade laser with the wavelength range from 4.7 to 4.9 μm. After the CO2 laser annealing with appropriate power, the propagation losses range measured for Ge core fibers with different core diameters were between 1.96 dB/cm to 2.36 dB/cm.