为了提高大模场面积光纤到单模光纤的耦合效率, 利用加热扩芯的方法, 对单模光纤进行了热扩芯处理, 实现了大模场面积双包层光纤15/130 μm到单模光纤6/125 μm的模式匹配。对进行热扩芯处理的模场匹配器的传输损耗进行了理论分析; 利用自行搭建的中心波长为1 064 nm的激光光源分别测量了商用及自制的模场匹配器的传输损耗。实验结果表明: 采用加热扩芯的方法极大地提高了大模场面积光纤到单模光纤的模场匹配器的模式耦合效率。与商用的模场匹配器相比, 自制的模场匹配器具有更高的耦合效率和运行功率, 其热处理能力更强, 可靠性也更好, 运行功率可以达到100 W; 在进行风冷的情况下, 稳定工作时间累计为120 min, 最终可以获得 73 W的单模光输出, 热处理能力为27 W。模场匹配器性能的提高满足了高功率光纤元器件发展的需要, 有利于实现光纤激光系统的全光纤化。

To improve the coupling efficiency for a Large-mode-area Fiber (LMAF) and a Single-mode Fiber(SMF), a Thermally Expanded Core (TEC) technique was used to expand the core of SMF to implement the mode field adaptation for the LMA double clad fiber 15/130 μm and the SMF 6/125 μm.The transmission loss of the Mode Field Adaptor(MFA) made by TEC processing was analyzed theoretically, and a homemade MFA and a commercial MFA was respectively measured through a self-built fiber laser source with a 1 064 nm central wavelength. Experiment results show that the TEC technique dramatically improves the coupling efficiency of the MFA between the LMA and the SMF. In contract with the commercial MFA, the homemade MFA is capable of a higher operating power, better heat treatment capacity and better reliability. The homemade MFA offers the operating power up to 100 W, and accumulated working time up to 120 min in an air-cooled condition. Furthermore, its single-mode output to be 73 W, and heat treatment capacity to be 27 W. The improvement of the performance of MFA meets the needs of the development of high-power fiber components and are suitable for achieving all-fiber-integration systems of fiber lasers.