大模场面积(LMA)光纤激光器的光束质量通常比单模光纤激光器的光束质量差。采用光纤拉锥的方法进行模式选择,从而提高大模场直径光纤激光器的光束质量。拉锥区距光纤激光器的输出端约5 mm,纤芯最小为9 μm,约为未拉锥部分纤芯直径26 μm的1/3。实验研究表明,在拉锥后,光纤激光器的光束质量因子M2由3.50减小为1.81,相应的斜率效率由63.6%减小为51.1%。虽然拉锥后最大输出功率减少了约19.8%,但其亮度增大为拉锥前的3倍。

For large-mode-area (LMA) fiber laser, the beam quality is not as good as that of single mode fiber laser. A tapered section was introduced to a LMA fiber. The core diameter of the smallest part was 9 μm, which was located 5 mm away from the output end of the fiber and about three times smaller than the conventional fiber core with the diameter of 26 μm. The experimental results show that the beam quality factor M2 is reduced from 3.50 to 1.81, with the slope efficiency from 63.6% to 51.1%. Although the tapering induces 19.8% power loss, the brightness of the tapered fiber laser is 3 times as much as that of the untapered.