大口径锥度光纤SBS种子注入的熔石英棒布里渊放大器特性

Characteristics of Fused Silica Rod Brillouin Amplifier Simulated Brillouin Scattering Seeded by Large Aperture Tapered Fiber

使用重复频率为400 Hz的Nd∶YAG单纵模主振荡器功率放大(MOPA)激光器作为光源,大口径锥度光纤作为受激布里渊散射(SBS)种子池产生SBS种子光,固体熔石英棒作为SBS放大池,对反向注入的SBS种子光在熔石英棒中呈现不同增益,也即不同抽运功率条件下的布里渊放大行为从功率、时间和空间三个大的方面进行了详细的实验研究,包括放大的SBS输出功率、注入SBS种子光放大倍率、总的SBS反射率、熔石英棒布里渊放大器提取效率以及脉冲宽度和光束质量随SBS种子注入功率的变化情况等。获得了最高输出15.5 W的放大SBS输出、70倍的SBS种子光放大倍率、大于50%的总反射率以及52%的能量提取效率;观察到脉冲展宽以及布里渊放大器中的增益导引两种现象。实验结果表明,在小信号SBS种子光和大信号SBS种子光注入情况下,熔石英棒布里渊放大器具有不同的放大特性。另外,在实验过程中还发现,SBS种子光和抽运光的空间重合程度以及熔石英棒中抽运功率密度的大小是影响SBS放大输出功率的两个重要方面。

Detailed experimental investigations on the amplification characteristics of back-injected simulated Brillouin scattering（SBS） seed laser in solid fused silica rod Brillouin amplifier under different pump power levels have been done,in which a master oscillator power amplifier（MOPA） single longitudinal mode Nd∶YAG laser with repetition rate of 400 Hz is used as pumping source,and a large aperture tapered fiber as SBS generator and solid fused silica rod as SBS amplifier.These characteristics include amplified SBS output power,amplification ratio of injected SBS seed laser,total SBS reflectivity,extraction efficiency of fused silica rod Brillouin amplifier,pulse width and beam quality versus SBS seed laser power.A maximum amplified SBS output power of 15.5 W,amplification ratio of 70,total SBS reflectivity of more than 50%,and extraction efficiency of 52% are obtained.Pulse width broadening and gain guiding have been observed.The experimental results indicate that the fused silica rod Brillouin amplifier has different amplification characteristics with small signal SBS seed laser and large signal SBS seed laser.Additionally,the degree of spatial superposition of SBS seed laser and pump laser and the pump power density in fused silica rod are found to be two important aspects which influence the amplified SBS output power.