高功率掺Tm^3+光纤放大器热效应管理的泵浦方式优化理论研究

Theoretical Study of Pumping Method of High Power Tm^3+-doped Fiber Amplifier for Thermal Effect Management

基于主振荡功率放大器结构的高功率掺Tm^3+光纤激光器是2μm波段高功率光纤激光器的主要实现形式,掺Tm^3+光纤放大器(Thulium-doped fiber amplifier,TDFA)热效应管理的研究对于其输出激光功率的不断提升具有重要意义。本文主要对TDFA热效应管理的泵浦方式优化方面进行理论研究,利用龙格库塔法以及牛顿迭代法求解不同泵浦方式下TDFA的稳态速率方程,并根据热传导方程,模拟掺Tm^3+光纤(Thulium-doped fiber,TDF)温度沿径向和轴向的分布。结合遗传算法理论,研究了分段泵浦方式,经过参数优化,在功率为5 W的2020 nm输入信号光、总功率为1000 W的793 nm激光泵浦、TDF吸收系数为3.1 dB/m条件下,将总长度为11 m的TDF分为2.4,2,2,2,2.6 m的5段进行泵浦,得到放大信号激光输出功率为284.5 W、斜率效率为28.45%、光纤外包层边界最高温度为86.28℃且温度总体分布均匀。与传统前向泵浦、双端泵浦方式下的TDFA相比,其热效应有明显改善。

The high-power thulium(Tm^3+)doped fiber laser(TDFL)based on the structure of master oscillator power-amplifier is the main type of 2μm band high-power fiber lasers.Study on thermal effect management of the thulium doped fiber amplifier(TDFA)stage means a lot to the continuously power-scaling of the TDFL.This paper mainly focuses on the theoretical research on the optimization of the pumping method of TDFA for thermal effect management.We use the Runge-Kutta method and Newton iteration method to solve the steady-state rate equation of TDFA under different pumping methods.And,on the basis of the heat conduction equation,the temperature distributions of Tm^3+doped fiber(Thulium-doped fiber,TDF)along the radial and axial direction are simulated.Combining with the genetic algorithm theory,the segmentally pumping method is studied.Through optimizing of the relative parameters,using a 2020 nm input signal light with a power of 5 W,a total 793 nm laser pump power of 1000 W and a TDF with an absorption coefficient of 3.1 dB/m and a total length of 11 m which is divided into 5 segments(2.4,2,2,2,2.6 m),we obtained an amplified signal laser with an output power of 284.5 W and a slope efficiency of 28.45%,and the maximum temperature at the outer cladding boundary of the TDF is only 86.28℃with a uniform temperature distribution along the whole fiber.Compared with a TDFA using traditional forward pumping or dual-end pumping mode,the thermal effect has been significantly improved.