高功率光纤放大器中的受激布里渊散射

Stimulated Brillouin scattering in high-power fiber amplifier

针对1～5ns短脉冲单纵模高功率放大器实验中观察到的受激布里渊现象，结合光纤放大器的速率方程以及受激布里渊散射瞬态特性的耦合振幅方程组进行了理论研究，采用时域有限差分的方法．对3ns、5ns两种脉冲进行模拟，讨论了短脉冲光纤放大器中受激布里渊散射的特性，结果表明：短脉冲的受激布里渊散射阈值远高于准连续脉冲的阈值，是高功率光纤放大器输出的主要限制因素，且光纤放大器中受激布里渊散射要比普通传输光纤增长要快，其强度跟脉冲脉宽和泵浦功率相关，实验结果与模拟结果吻合较好。最后提出了几种抑制高功率光纤放大器中受激布里渊散射的方法。

Aiming at the stimulated Brillouin scattering （SBS） occurred in high-power single-frequency fiber amplifier with 1-5 ns pulse width. New model which was combined rate equation for fiber amplifier and the coupled-ampl.itude equations was used in this paper, simulations for 3 ns and 5 ns pulse were obtained based on the method of finite-difference time-domain. The characteristic of SBS in high-power single-mode fiber amplifier was discussed. The experimental results show that the SBS is the main limiting factor for the output of the fiber amplifier, and the threshold of the SBS for short ＂pulse was much higher than that for quasi-continuous pulse. The simulation shows that SBS in fiber amplifier increasing more quickly than the transmission fiber when the laser intensity exceeds the SBS threshold, and the SBS intensity was related with the pulse width and the pump power, which has a good agreement with the experiment. Finally, the methods for suppressing of SBS were presented.