1µm Kilowatt-Scale MOPA Structure All-Fiber Laser

The MOPA structure has become one of the mainstream medium and high power fiber laser designs due to its advantages of good beam quality and adjustable parameters. This paper proposes a kilowatt-scale MOPA structure fiber laser based on a 915nm pump laser and a 14/250 ytterbium-doped fiber. The effects of low reflection grating, gained fiber length, and splice loss on the photo-to-optical conversion efficiency of the resonator are discussed, and the factors that affect the overall photo-to-optical conversion efficiency of the MOPA structure are further discussed. The matching relationship between the power of seed fiber and the pump power of the amplifier stage is experimentally studied. The results show that the optical-to-optical conversion efficiency of the resonator can be approached to the theoretical level by optimizing the parameters. When the power of the seed is about 10% of the pump power of the amplification stage, the ASE of the amplification stage can be effectively suppressed, and the overall structured conversion efficiency of MOPA is optimal. According to the results, an all-fiber MOPA fiber laser with an output power of 1040W was realized. The optical-to-optical conversion efficiency and spectral characteristics were consistent with the analysis. This paper provides a design idea for a higher power MOPA fiber laser.