Effect of CO2 laser annealing with different laser frequencies on Ge core fiber

Abstract

The germanium (Ge) core fibers via molten core drawing (MCD) method were annealed by CO2 lasers of 30 kHz, 50 kHz and 70 kHz frequencies respectively under the same laser output power condition. The effect of different laser frequencies on the Ge fiber was mainly investigated using Raman frequency maps, propagation loss measurement and Energy dispersive X-ray spectroscopy (EDS). Raman frequency maps show that the optimization effect of 50 kHz laser annealing on Ge core properties is significantly better than that of 30 kHz and 70 kHz lasers. For the samples annealed by 30 kHz, 50 kHz and 70 kHz lasers, the lowest propagation loss obtained in each laser frequency is 4.598 dB/cm, 2.102 dB/cm, and 2.873 dB/cm respectively, which were measured using a quantum cascade laser with the wavelength range from 4.7 to 4.9 μm. The results of this study indicate that the laser frequency had a significant impact on the properties of Ge core during the process of CO2 laser annealing.