基于主振荡功率放大器, 采用1120 nm光纤激光器作为种子激光, 将其注入20 m大模场面积单模双包层掺Yb光纤放大器, 并用976 nm半导体激光器泵浦实现了1 120 nm信号光输出.实验中将注入种子激光功率预设为10 mW, 当半导体激光器泵浦功率增大至1.5 W时, 放大器系统开始输出1 120 nm信号光.当泵浦功率低于3.4 W时, 信号光功率随泵浦功率缓慢增长, 系统斜率效率较低; 而当泵浦功率高于3.4 W时, 信号光功率随泵浦功率线性增长, 斜率效率明显增大, 达到48.5%.限于最大注入泵浦功率为6.8 W, 放大器输出最高1 120 nm信号光功率为1.97 W, 总的光-光转化效率为29%.输出信号光中心波长为1 120.89 nm, 线宽为0.02 nm, 极好地保持了种子激光的特性.结合实验情况, 利用双包层光纤放大器的稳态理论模型, 采用有限差分方法模拟了放大器输出信号光功率随泵浦光功率的变化曲线, 结果显示理论模拟所得变化趋势与实验结果吻合良好, 系统将在泵浦功率达到200 W左右时达到饱和状态, 说明目前光纤放大器系统具有很大的功率提升空间.

Based on master oscillator power amplifier regime, a 976 nm laser diode pumped 20-m-long single-mode double-clad large-mode-area ytterbium-doped fiber amplifier at 1 120 nm was experimentally demonstrated.In the experiment, the injected power of the fiber seed laser was set to be 10 mW.When the diode laser pump power is increased to 1.5 W, the amplifier system begins to emit signal laser at 1 120 nm.The experimental results reveal that the signal output power increases slowly under low pump power level, however, when the pump power is beyond 3.4 W, the slope efficiency increases fleetly to 48.5%.Limited to the available launched pump power of 6.8 W, a maximum output power of 1.97 W is achieved.The total optical-to-optical conversion efficiency of the system is 29%.The measured center wavelength of the output signal laser is 1120.89 nm with a linewidth as narrow as 0.02 nm, which well preserves the characteristics of the seed laser.According to the parameters of the optical devices in the experiment, based on the steady-state-model of the double-cladding fiber amplifier and finite-difference-method, the relationship of the output signal power versus the diode laser pump power is theoretically calculated.The comparison between the experimental results and the theoretical results displays that the growth trend of the output signal laser power kisses well with the theoretical model.The system will be saturated when the pump power beyond 200 W, which reveals that the amplifier has a large space of power scaling up.