窄线宽1064 nm掺镱光纤激光器泵浦MgO:PPLN中红外光学参量振荡器研究

提出了一种基于1064 nm掺镱光纤激光器泵浦MgO:PPLN的3.83 μm中红外光学参量振荡器。基于单谐振光学参量振荡器的阈值理论和线宽压窄前后的光束能量集中性理论，分析了不同泵浦光束聚焦深度下，谐振腔内光束分布情况以及线宽调制前后能量的不同集中程度对阈值和光-光转换效率所产生的影响。通过采用单个光纤布拉格光栅的方式压窄了泵浦光线宽，对比分析了在不同占空比下，泵浦光线宽压窄前后对中红外光学参量振荡器输出特性的影响。当泵浦功率为18 W，脉冲激光占空比为0.2%，脉宽为100 ns，泵浦光线宽为2.5 nm时，MgO:PPLN中红外光学参量振荡器获得功率为1.42 W的3.83 μm激光输出，光-光转换效率为7.9%。将线宽压窄到0.1 nm后，脉宽为2 ns，MgO:PPLN中红外光学参量振荡器获得最高功率为1.98 W的3.83 μm激光输出，光-光转换效率为11%，光束质量M2=1.89；同时相比于线宽压窄前激光输出效率提高了39.2%。

Study on mid-infrared optical parametric oscillator based on MgO:PPLN pumped by narrow linewidth 1064 nm fiber laser

A 3.83 μm mid-infrared optical parametric oscillator based on 1064 nm Yb-doped fiber laser pumped MgO:PPLN is proposed. Based on the threshold theory of single resonant optical parametric oscillator and the beam energy concentration theory before and after linewidth narrowing, the effects of the beam distribution in the resonant cavity and the different energy concentration levels before and after linewidth modulation on the threshold and optical-optical conversion efficiency under different pump beam focusing depths are analyzed. By using a single fiber Bragg grating to narrow the pump light width, the influence of the pump light width on the output characteristics of the mid-infrared optical parametric oscillator is analyzed under different duty ratios. When the pump power is 18 W, the pulse laser duty cycle is 0.2%, the pulse width is 100 ns, and the pump light width is 2.5 nm, the MgO:PPLN mid-infrared optical parametric oscillator obtains 3.83 μm laser output with a power of 1.42 W, and the optical-optical conversion efficiency is 7.9%. When the linewidth is narrowed to 0.1 nm and the pulse width is 2 ns, the infrared optical parametric oscillator in MgO:PPLN achieves 3.83 μm laser output with the highest power of 1.98 W. The optical-optical conversion efficiency is 11% and the beam quality M2=1.89. At the same time, the laser output efficiency is increased by 39.2% compared with that before linewidth narrowing.