水中受激布里渊散射微弱Stokes信号光的高增益放大

采用脉冲宽度为7.2 ns的种子光注入式倍频Nd:YAG脉冲激光器，以CS₂为放大介质，实验并理论研究了水中受激布里渊散射微弱Stokes光的信号增益随延迟时间、放大器池长、抽运光能量的变化规律. 结果表明，当抽运光脉冲相对信号光脉冲延迟进入放大器，且延迟时间为脉冲宽度的一半，抽运光能量略低于介质受激布里渊散射阈值，选择合适的放大器池长可获得最佳的信号增益. 适当选择抽运光能量，亦可实现微弱信号光的线性放大. 实验中采用独立双池放大系统，当水中Stokes信号光的能量为1 pJ时，信 关键词： 布里渊放大器 信号增益 延迟时间 抽运光能量

High-gain amplification of weak Stokes signal of stimulated Brillouin scattering in water

The influences of the delay time, the cell length and the pump energy on the gain amplification of weak Stokes signal of stimulated Brillouin scattering (SBS) in water are investigated theoretically and experimentally. In the experiment a frequency-doubled seed injection Nd:YAG laser with a pulse duration of 7.2 ns was used. Results showed that the pump pulse should lag the Stokes signal pulse by an amount equal to pulse half-width to obtain the maximum gain. Depending on the pump energy the signal below 10^-5 mJ is linearly amplified. By using CS₂ as amplifier medium, a Stokes signal of 1pJ from water is amplified with high gain (7×10⁷) in the regime below the pump's self-SBS threshold.