对主振荡功率放大器(MOPA)方式脉冲抽运双包层掺镱脉冲光纤放大器进行了理论研究, 分析了放大中抽运脉冲、激光脉冲和拉曼斯托克斯光脉冲的相互作用过程。对增益光纤中上能级粒子数密度随抽运时间的变化进行了分析, 求出了最佳抽运脉冲宽度。随着抽运功率的增加, 放大过程中出现的受激拉曼效应(SRS)将抑制激光脉冲能量的增加, 当采用最佳抽运功率时激光脉冲的能量可达到最大值。分析了光纤长度、纤芯直径对最佳抽运功率、激光脉冲和一级斯托克斯光脉冲的影响。结果表明, 当最佳抽运功率时, 采用纤芯较粗、长度较短的增益光纤, 可以抑制受激拉曼效应, 提高激光脉冲的能量与峰值功率。

A theoretical analysis is made on pulse pumped double-clad Yb-doped fiber amplifier based on master oscillator power-amplifier(MOPA). The interaction processes of the pumping pulse, laser pulse and Raman Stokes optical pulse during the fiber amplification have been analyzed. The change of the upper level population density of the gain fiber with the pumping duration is simulated, and the optimal pumping pulse width is found. With the pumping power increasing, the stimulated Raman effect appeared during the amplification process will restrain the signal pulse energy. The signal pulse energy can reach the peak under the optimal pumping power. The effect of the fiber length and core diameter on the optimum pumping power, laser pulse and first-order Stokes optical pulse is analyzed too. Results show that when the pumping power is the optimum, the bigger core and shorter length fiber should be used in the fiber amplifier in order to increase the signal pulse energy and peak power as much as possible.