国产光纤实现同带抽运3000W激光输出

同带抽运是目前实现高功率光纤激光器的有效手段.本文基于同带抽运方式,以国产25/250μm掺镱双包层光纤为增益光纤,构建了全光纤化的主控振荡器功率放大器.实验中采用的国产光纤是中国电子科技集团公司第四十六研究所采用化学气相沉积结合气相-液相复合掺杂工艺制备的,其Yb~(3+)离子的分布更均匀,吸收截面更大,吸收系数更高.实验中,在种子光功率为67.8 W、抽运总功率为3511 W的条件下,实现了3079 W的激光输出,斜效率为85.9%,光束质量M~2约为2.14,3dB带宽为1.4nm,这是目前基于国产光纤同带抽运方式实现的最高功率.理论和实验结果表明国产光纤制备技术不断成熟,已经具备承受高功率输出的能力.继续提高抽运功率,优化增益光纤长度,改良散热方式,国产光纤有望实现更高功率的激光输出.

3000 W tandem pumped all-fiber laser based on domestic fiber

In recent years, high power fiber laser has received great attention, leading to wide applications in numerous fields such as industry, biology and relevant research. Nevertheless, the output power of typical diode pumped fiber laser is limited by the thermal effect and brightness of pump source. Owing to the low quantum deficit, the tandem pumping employing ytterbium-doped fiber lasers (YDFLs) as the pumping source can effectively reduce the thermal issue and achieve high power output. With the much lower absorption coefficient at 1018 nm than at 976 nm, longer gain fiber is necessary in tandem pumped configuration to sufficiently absorb pump light, which in turn induces a more severe nonlinear effect such as the stimulated Raman scattering, bringing in more challenges in laser configuration design. In this paper, we demonstrate an all-fiber laser under master oscillator power amplifier configuration based on tandem pumping with domestic gain fiber produced by China Electronics Technology Group Corporation No. 46 Research Institute. The diameters of the core and inner cladding of the Yb³⁺ doped double cladding fiber are 25 μm and 250 μm, respectively. The modified chemical vapor deposition method with gas-solution co-doping method is adopted so that the fiber has a more uniform distribution of Yb ions, larger absorption cross section and higher absorption coefficient (0.41 dB/m@1018 nm). In the amplifier stage, a 40-m-long gain fiber is pumped by fourteen 1018 nm fiber lasers with a maximum total output power of 3511 W. A 67.8 W 1080 nm seed is amplified to 3079 W with a corresponding slope efficiency of 85.9%. The beam quality factor M² is measured to be 2.14. In addition, no stimulated Raman scattering is found in output spectrum and the 3 dB band width of output laser is measured to be 1.4 nm. To the best of our knowledge, this marks the highest result ever reported for tandem pumping based on domestic gain fiber. Taking stimulated Raman scattering into account, the rate equations are built to calculate the properties and power evolution in the fiber amplifier. The numerical results are in good agreement with the experiment results. Besides, based on heat conduction equation, heat power density in the fiber core is analyzed, showing that the tandem pumping has great advantages in heat management and a huge potential to reach a higher power compared with the method of direct pumping. The theoretical and experimental results show that with ever-maturing fiber manufacturing technology, domestic fiber is capable of withstanding laser power as high as 3 kilowatts. Meanwhile, domestic fiber may achieve a higher output power by increasing the pump power, optimizing the gain fiber length and improving the cooling condition.