采用高功率975 nm多模半导体激光器(LD)作为抽运源, 以大模场掺Yb3+双包层光纤(YDCF)作为激光增益介质, 运用能够承受较高功率运行的利特罗(Littrow)光栅外腔调谐结构, 实现了宽带可调谐激光输出。实验中, 双包层光纤采用最优光纤长度14 m, 光栅经仔细调整后有效入纤反馈效率约20%, 当入纤抽运功率约1.3 W时, 激光器达到阈值并开始振荡。通过连续旋转光栅, 激光输出波长能在1046～1121 nm之间实现可调谐, 可调范围达75 nm。当入纤抽运功率为48 W时, 在1089 nm波长处获得最大输出功率23.7 W, 相应斜率效率为53%。最后, 基于数值模拟简单地分析了激光输出特性, 实验结果与数值模拟结果基本保持一致。

A tunable Yb3+-doped double-clad fiber (YDCF) laser has been demonstrated experimentally using a high-power 975 nm laser diode (LD) as the pump source, a large-mode-area YDCF as the gain medium and a blaze grating-based Littrow configuration as the tunable mechanism. With the optimal fiber length of 14 m and the effective reflectivity 20% of the blaze grating, the threshold pump power of the laser is ～1.3 W. Through rotating the blaze grating, the output lasing wavelength can be broadly tuned from 1046 nm to 1121 nm. When the injected pump power is 48 W, a tunable output of 23.7 W at 1089 nm is achieved with a slope efficiency of 53%. Numerical simulation is performed to analyze the laser output characteristics, and the experimental results are in good agreement with those by numerical simulation.