为了研究低重复频率两级脉冲掺Yb3+光纤放大器,采用脉冲信号驱动的半导体激光器作为种子光源,产生重频100Hz、半峰全宽100ns、能量30nJ的矩形光脉冲。第1级放大采用单模掺Yb3+光纤放大器,双程放大方案有效地抑制了放大自发辐射,放大后的脉冲能量达到了8.2μJ。第2级放大采用纤芯直径15μm的双包层掺Yb3+光纤放大器,大功率多模半导体激光器连续抽运。结果在抽运功率为7.3W时,放大输出脉冲能量达到了242μJ,放大输出半峰全宽压缩为29ns。输出的光束质量较好,为准单模输出。结果表明,该光纤放大器输出脉冲能量高,具有全光纤化、结构简单的特点。

In order to study a two-stage Yb³⁺-doped fiber amplifier for low repetition frequency pulses,a pulse driven laser diode was used as the seed source to obtain rectangle optical pulses with repetition rate of 100Hz,full width at half maximum(FWHM) of 100ns and energy of 30nJ.In the first stage,8.2μJ pulse energy was obtained by a single mode Yb³⁺-doped fiber amplifier,in which amplified spontaneous emission was restrained efficiently by means of the method of round-trip amplification.Pumped by 980nm high power multimode laser diodes,the second stage was a double clad Yb³⁺-doped fiber amplifier with 15μm fiber core diameter.242μJ output pulse energy was obtained at 7.3W pump power.The FWHM was compressed to 29ns.A near diffraction limited beam was produced from the amplifier with quasi-single mode output.The results shows that the high pulse energy fiber laser has advantage of simple all fiber structure.