Utilizing a GeO2 optical fiber for a 2.79 μm Er:LuYSGG CW laser transmission

We demonstrate the transmission of 2.79 mu m continuous-wave (CW) Er:LuYSGG laser energy with a high coupling efficiency by a GeO2 fiber for the first time. Based on the parameters of the Er:LuYSGG laser, a 2.79 mu m laser and GeO2 fiber coupling system is designed and constructed. The reasons for the decrease in coupling efficiency with increasing input power are analyzed. The transmission efficiency of the CW laser under different bending radii of the fiber is measured, and the fiber exhibits a low bending loss. Even at the smallest bending radius (R = 50 mm), the fiber still maintains over 81 % transmission efficiency and a maximum outpower of 399.2 mW. The beam profiles at the output end-face of the fiber reveal that the multimode fiber has a beam-shaping effect on the incident beam. Although the beam quality decreases, the energy distribution of the laser beam becomes more uniform. This work is expected to further promote the practical applications of mid-infrared (MIR) lasers and provide a valuable reference for future coupling studies between solid-state lasers and fibers.