激光二极管抽运电光调Q双通激光器中的光纤相位共轭

Fiber Phase Conjugation in Laser Diode-Pumped,Electrooptical Q-Switched Laser with Double-Pass Amplifier

为了降低高重复频率脉冲固体激光器中热致光束畸变对光束质量的影响 ,在激光二极管抽运、电光调Q的Nd∶YAG激光双通放大系统中对多模石英光纤相位共轭镜进行了实验研究。激光重复频率 10 0Hz、脉宽 2 0ns。实验结果表明 :应用多模光纤能够显著改善放大级中热效应引入的波面畸变 ,双通获得近衍射极限的激光输出 ,并可大幅度压缩脉宽至 7ns,达到了 3∶1的压缩比。在受激布里渊散射阈值附近 ,实验中观察到相位共轭光光斑剧烈闪烁 ,而随着注入光纤能量的增大 ,闪烁现象渐渐消失 ,输出激光能量的稳定度提高 ,在注入能量 5 .3mJ的情况下 ,获得了 14 %的能量不稳定度 ,此时的反射率和退偏率分别为 32 .6 %和 7%。

To reduce the thermal effect to beam quality in solid state laser with high repetition rate, multimode optical fiber as phase conjugator has been experimentally investigated in an laser diode\|pumped, electrooptical Q switched Nd∶YAG laser with double pass amplifier. The laser was operated on 100 Hz repetition rate and 20 ns pulse width. Perfect correction of laser profile distortion in amplifier and beam quality close to diffraction limit has been achieved. Pulse width of phase conjugated laser was compressed to 7 ns while compression ratio reached 3∶1. Beam glitter has also been observed in lower pumping energy close to stimulated Brillouin scattering (SBS) threshold. With increase of energy coupled into fiber, that phenomenon was weakened, and higher stability was achieved. In the case of 5.3 mJ input energy, instability less than 14% is obtained, while SBS reflectivity and depolarization ratio were 32.6% and 7% respectively.