利用双包层掺镱光子晶体光纤(DC-PCF)作为增益光纤, 设计制作了全光纤双包层光子晶体光纤放大器。实验制作了匹配DC-PCF的(6+1)×1端面抽运耦合器, 6根抽运光纤采用包层直径、纤芯直径分别为105 μm和125 μm（数值孔径为0.22）的多模光纤, 信号光纤采用普通单模光纤。利用套管法制作端面抽运耦合器, 并将制作完成的耦合器与DC-PCF直接熔接, 再对光子晶体光纤进行锥棒熔接, 锥棒输出端面镀1000~1100 nm的增透膜, 以防止激光反馈对整个放大系统产生影响。对全光纤双包层光子晶体光纤放大器进行测试, 使用976 nm的抽运源提供能量, 信号光使用波长为1064 nm、功率为2 W的连续光。当抽运功率达到最大值151.83 W时, 最大输出功率为108.1 W, 斜率效率为72.7%。输出光斑为很好的基模光斑, 体现了光子晶体光纤在具有大模场面积的同时仍能保持基模传输的优良特性。

An all-fiber double-cladding photonic crystal fiber amplifier is designed and built, and the Yb-doped double-cladding photonic crystal fiber (DC-PCF) is used as the gain fiber. In the experiment, a (6+1)×1 end-pump coupler is fabricated to match the DC-PCF with six multi-mode fibers as pump fibers and ordinary single-mode fiber SMF-28 as the signal fiber. The cladding diameter and the core diameter is 105 μm and 125 μm respectively, and the numerical aperture is 0.22. An end-pump coupler is fabricated by the capillary tube method and directly spliced with DC-PCF. At last, the DC-PCF is spliced with a tapered end-cap. The end-cap is plated with 1000-1100 nm anti-reflective coating film to prevent the entire amplification system from the effect of laser feedback. The designed amplifier is tested with pump light at the wavelength of 976 nm and continuous signal of 2 W at 1064 nm. When the pump power reaches the maximum of 151.83 W, the maximum output power is 108.1 W and the slope efficiency is 72.7%. The output spot is a good fundamental mode spot. It indicates the excellent characteristics of the photonic crystal fiber, which can simultaneously maintain the large mode field and the fundamental mode transmission.