利用改进的化学气相沉积工艺结合溶液掺杂技术制备了高光束质量的25/400 μm双包层掺镱光纤。石英纤芯的掺杂组分为Yb2O3、Al2O3、P2O5,Al2O3有助于降低Yb3+团簇, 增加Yb3+掺杂浓度, P2O5起到降低光子暗化效应的作用。纤芯-包层折射率差为0.001 2, 纤芯的数值孔径为0.06。976 nm波长处的包层吸收系数为2.1 dB/m。构建双向抽运方式的主控振荡器功率放大器结构对增益光纤性能进行测试。实验中, 1 080 nm种子光功率为235 W, 在抽运光总功率为3 706 W时, 实现了最大功率3 243 W激光输出, 斜效率为81.1%, 光束质量因子β为1.7, 未发生受激拉曼散射现象。光纤激光器连续工作1 h, 输出功率未见明显变化。采用相同测试方法及平台对25/400 μm型号的进口光纤进行测试, 对比实验结果表明: 实验中制备的双包层掺镱光纤主要性能指标已接近进口光纤。

A high power 25/400 μm ytterbium doped double-cladding fiber(YDF) with excellent beam quality was successfully fabricated by MCVD in conjunction with solution doping technology. The dopants of the silica fiber core include Yb2O3, Al2O3 and P2O5. Al2O3 could reduce the clustering of Yb3+ and increase the doping concentration. P2O5 was helpful to restrain photodarkening phenomenon. The core-cladding refractive index difference is 0.001 2, corresponding to the core numerical aperture of 0.06. The value of the cladding absorption is 2.1 dB/m at 976 nm. Master oscillator power amplifier configuration based on two end pump was constructed to test the Yb-doped fiber performance. In the experiment, the power of the 1 080 nm seed is 235 W, the total power of the pump power is 3 706 W. The maximum output power is 3 243 W with a slope efficiency of 81.1%. The beam quality factor β was measured to be 1.7. Stimulated Raman scattering(SRS) has not been found in the output laser spectrum. The fiber laser continues to work for one hour, the output power is stable at 3 240 W. In addition, a kind of 25/400 μm imported fiber was tested in the same experiment schematic. Comparative experimental results show that the performance of the domestic fiber is close to the imported fiber.