이터븀이 첨가된 광섬유 레이저 제작과 특성에 관한 연구

Abstract

We have demonstrated all fiber laser consisting of Yb-doped fiber, fiber Bragg grating mirrors, a fiber bundle combiner and a pigtailed laser diode. The used fiber bundle combiner have branches of 7 fibers coupled with the pump LD of 8 W. The double cladding fiber have a core diameter of 10 μm and a cladding diameter of 125 μm. The shape of the inner cladding was designed to be octagonal to improve a pumping efficiency. Two Bragg reflectors have the reflectance of >99% and 5%, respectively. To get the optimum conditions for lasing the fiber laser, we investigated numerically the dependence of the output power on reflectance of Bragg mirrors and fiber length. Under the condition of the splice loss of 0.22 dB, the optimum fiber length was 9 m at 5%- and 99%-reflectance of the Bragg mirrors. So we constructed a Yb-doped fiber laser with the length of 9 m. The designed laser had the output power of 12 W at the pump power of 25 W. The slope efficiency was 49%. We investigated the bending effects of the fiber laser. We found that the designed laser have the decrease of the output power when the bending diameter became to be less than 20 cm.