国产纺锤形渐变掺镱光纤实现6 kW宽谱激光输出

高功率高光束质量光纤激光器在工业加工等领域有着广泛的应用，然而光纤中的非线性效应和模式不稳定效应限制着高光束质量光纤激光器的功率提升，采用新型结构大模场增益光纤在同时抑制非线性效应和模式不稳定效应方面具有较大潜力。报道了基于单位自研的纺锤形渐变掺镱光纤激光成功实现6 kW功率、高光束质量激光输出。激光器采用主振荡功率放大结构，放大级采用双向981 nm泵浦纺锤形渐变掺镱光纤，在总泵浦功率为7.68 kW时，输出功率达到6.02 kW，光束质量M2因子约为1.9。通过进一步优化纺锤形掺镱光纤制作工艺及结构参数，有望实现更高功率、近单模光束质量的光纤激光输出。

6 kW broadband fiber laser based on home-made ytterbium-doped fiber with gradually varying spindle-shape structure

High power fiber lasers with high beam quality have been widely employed in applications of industrial manufacture. However, the power scaling of the fiber lasers with high beam quality are limited by the fiber nonlinear effects and the transverse mode instability. It is promising to simultaneously mitigate the fiber nonlinear effects and transverse mode instability by employing large mode area gain fiber with novel structure. In this letter, we report a 6 kW fiber laser with high beam quality, which is realized based on home-made ytterbium-doped fiber with gradually varying spindle-shape structure. The fiber laser employs the master oscillation power amplification structure. In the stage of laser amplifier, spindle-shape ytterbium-doped fiber is bidirectionally pumped by laser diodes with 981 nm wavelength. At the total pump power of 7.68 kW, the maximum output power reaches 6.02 kW with a beam quality M2 factor of 1.9. By optimizing the manufacture techniques and structure parameters of the spindle-shape ytterbium-doped fiber, it is promising to achieve fiber lasers with higher power and nearly single mode beam quality.