三倍频Nd∶YAG激光抽运氧气中的受激拉曼和布里渊散射

报道了三倍频脉冲Nd∶YAG激光(355 nm)在两种不同带宽模式下抽运氧气中受激拉曼散射(SRS)和受激布里渊散射(SBS)的实验研究。在宽带(约1 cm-1)抽运模式下,只测到了前向受激拉曼散射,而没有观察到后向散射,其一级和二级斯托克斯最大能量转换效率可达22%和8%。在窄带(约0.003 cm-1)模式下,前向、后向受激拉曼散射和受激布里渊散射都测量到了,但大部分抽运能量都转换到受激布里渊散射,其转换效率可达67%。测量了两种带宽模式下各散射组分在它们最佳转换时的波形;窄带情况下后向受激拉曼散射和受激布里渊散射的脉宽分别可压窄至1.5 ns和2.3 ns,不到抽运脉宽的三分之一,使得受激布里渊散射峰值功率可大大高于抽运功率。对氧气中前向、后向受激拉曼散射和受激布里渊散射之间的竞争进行了讨论。

Stimulated Raman and Brillouin Scattering in Oxygen Pumped by a Nd∶YAG Laser at 355 nm

Experimental results of reported stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in oxygen pumped by a pulsed Nd∶YAG laser at 355 nm in two different bandwidth cases are reported. In broad band (～1 cm-1) case, only forward SRS was measured while backward scattering was not observed. Maximum energy conversion efficiencies of 22% and 8%, respectively for the first and second Stokes, were obtained. In narrow band (～0.003 cm-1) case, both forward and backward SRS and SBS were observed, but most of input pump energy was converted to SBS with conversion efficiency of 67%. The pulse shapes of various scattering components were measured in these two cases. In narrow band case the pulse width for backward SRS and SBS were respectively narrowed to 1.5～2.3 ns, no more than 1/3 of input pump pulse width, so SBS peak power was much larger than that of pump laser. The competition among forward and backward SRS and SBS in oxygen was discussed.