大模场掺铥光纤增益特性研究

为了进一步提升光纤激光器的输出功率，采用大模场面积掺铥光纤来抑制非线性效应，利用非均匀布喇格掺铥光纤结构，通过优化参量，在满足单模传输条件下获得模场面积为719μm2的大模场面积光纤。基于此光纤建立了793nm波长抽运下大模场掺铥光纤放大器理论模型。由于大模场面积光纤能降低光功率密度，抑制Stokes光功率，因此该种光纤放大器在高抽运功率下相比普通单模光纤放大器能够得到更大的输出功率。结果表明，当抽运光功率为100W时，所设计大模场面积光纤与普通单模光纤相比，转换效率提高5%，达到40%，输出功率达到41.01W。以上研究对于实际掺铥光纤放大器的设计有重要应用价值。

Study on gain characteristics for large-mode-area thulium-doped fibers

In order to enhance output power of a fiber laser, thulium doped fiber with large mode area was used to suppress the nonlinear effect. Optimizing parameters of a thulium-doped fiber in an inhomogeneous Bragg structure, a fiber with mode area of 719μm2 was obtained under the condition of single-mode transmission. Based on this fiber, a theoretical model for large mode area thulium-doped fiber amplifiers pumped by 793nm wavelength was established. Because large mode area fiber can reduce optical power density and suppress Stokes light power, compared with the ordinary single-mode fiber amplifier, this kind of fiber amplifiers under high pump power can get higher output power. The results show that, when pump power is 100W, compared with the conventional single-mode fiber, the conversion efficiency increases 5% and reaches 40%, and the output power reaches 41.01W. The research is of great value for design of actual thulium-doped fiber amplifiers.