单模光纤激光极限功率的数值研究

对光纤激光极限功率的探索和其受限因素的分析, 有利于为大功率光纤激光器的发展提供理论依据和实验指导. 本文考虑热效应、光效应、非线性效应和抽运亮度等因素对光纤激光极限功率的影响, 分析了掺镱和掺铥光纤的极限功率和受限因素. 在此基础上, 结合激光在光纤中单模传输的条件, 计算了单模掺镱和掺铥光纤激光的极限功率. 计算结果表明, 在现有技术条件下, 使用常规的976 nm和793 nm激光二极管抽运, 单模掺镱和掺铥光纤激光的极限功率分别为4.2 kW和7.8 kW, 其中单模掺铥光纤激光的功率水平还远低于它的极限功率的原因是受抽运亮度的限制. 最后分析指出减小纤芯的数值孔径和改进少模光束的光束质量是提升单模光纤激光极限功率的重要途径.

Numerical study on power limit of single-mode fiber lasers

Study on power limit of fiber lasers and analysis of their physical limits are helpful to develop high power fiber lasers both in theory and in experiment. In this paper, power limits and physical limits of ytterbium-doped and thulium-doped fiber lasers are analyzed by considering several limits to the power scalability of fiber laser, including thermal effect, optical effect, nonlinear effect and the brightness of pump source. Then combining these considerations with the basic requirement for single-mode fiber, the power limits of single-mode ytterbium-doped and thulium-doped fiber lasers are calculated. It is found that using traditional 976 nm and 793 nm laser diodes, separately, as a pump source, based on current technical conditions, power limits of single-mode ytterbium-doped and thulium-doped fiber lasers are 4.2 kW and 7.8 kW, respectively. It is concluded that the fact that the actual power presented by the single-mode thulium-doped fiber laser is much lower than its limit power is due to the pump brightness limitation. Finally the principal approaches to enhancing power limits of single-mode fiber lasers are summarized, including reducing numerical aperture of fiber core and improving beam quality of few-mode fiber lasers.