反共振空芯光子晶体光纤(HC-PCF)在中红外光纤气体激光器中具有重要的应用价值, 其与实芯光纤的低损耗耦合是实现全光纤结构光纤气体激光器的关键技术。采用将实芯光纤拉锥后插入空芯光纤的方案开展研究。理论和实验结果表明, 利用光纤拉锥处理技术改变普通光纤模场直径, 可使拉锥光纤与空芯光纤的模场直径近似匹配, 从而实现实芯光纤与大模场直径反共振HC-PCF的低损耗耦合。对于模场直径约为35 μm的Ice-cream型反共振HC-PCF, 仿真结果表明, 当锥腰直径为30~50 μm时, 耦合效率高于95%, 最高可达98%, 实验测得锥腰直径为35 μm时的耦合效率为96.05%。该结论为大模场直径空芯光纤与实芯光纤的低损耗耦合和实现全光纤结构气体激光器的全光纤化提供了一条可行的技术途径。

Anti-resonant hollow-core photonic crystal fibers (HC-PCF) have important application in middle-infrared fiber gas lasers. The low-loss coupling between HC-PCF and solid-core fiber is a key technology to realize all-fiber structure fiber gas lasers. A scheme of inserting tapered solid-core fibers into hollow-core fibers is proposed and studied. Theoretical and experimental results show that the low-loss coupling between solid-core fiber and anti-resonant HC-PCF with large mode field diameter is realized when we use optical fiber taping technology to change the diameter of ordinary fiber mode field and make the mode field diameter of the tapered fiber approximately match that of the hollow-core fiber. For the ice-cream type anti-resonant HC-PCF with mode field diameter of about 35 μm, the simulation results indicate that when the waist diameters of tapered fibers are around 30-50 μm, the coupling efficiency is over 95% and the maximum coupling efficiency can reach to 98%. In the experiment, the coupling efficiency is 96.05% when the waist diameter of tapered fibers is 35 μm. This conclusion provides a feasible technical approach for the low-loss coupling between anti-resonant HC-PCF with large mode field diameter and solid-core-fiber and the realization of all-fiber structure gas lasers.