采用布里渊噪声起源模型,数值研究了非聚焦条件下CS2液体介质中脉冲传输的能量与功率特性.结果表明,在非聚焦条件下,透射光的功率波形仍然表现出光限幅特性,而透射能量随入射能量线性变化,不具有限幅特性,这一点与聚焦条件下的结果不同.以波长1053nm、脉宽20ns的Nd:YLF激光器为光源,采用3∶1的缩束系统,通过衰减片调整入射光能量在2mJ-92mJ变化,获得了透射光能量和功率波形随入射能量变化的规律,并与聚焦条件下的结果进行了比较.实验结果与理论模拟相符合.由于聚焦条件下当入射能量较高时容易出现介质光学击穿,所以采用缩束结构的功率限幅更适用于高功率大能量的情况.
Adopting noise initiation model of stimulated Brillion scattering (SBS), the characteristic of transmitted energy and power in CS2 liquid media under non-focusing pump is investigated numerically. The results show that, the waveform of transmitted pulse with increasing input energy shows the characteristic of power limiting. And the transmitted energy varies linearly with input energy withont the energy limiting effect. When 1053 nm 20 ns Nd:YLF laser was used as pump in a 3∶1 inverse expansion system are using attenuators to adjust input energy in the rang of 2 to 92 mJ, the rules of transmitted energy and waveform versus input energy are acquired, and compared with the results of focusing pump. The experimental results are in good agreement with the theoretical simulations. Because the optical breakdown takes place at high input energy under focusing pump, the power limiting with non-focusing pump is applicable under the circumstances of high power and energy.