抽运光参数对受激布里渊散射的影响

Influence of pump laser parameters on stimulated Brillouin scattering

受激布里渊散射(SBS)系统中,具有一定带宽的抽运激光中会含有一定比例的Stokes散射光成分,此Stokes散射光成分经SBS介质后表面反射后,将形成种子光与抽运光联合入射,构成自种子光式SBS放大器.通过数值求解此SBS放大器型耦合波方程组,探讨了抽运光脉冲中所含Stokes散射光成分的比例、抽运激光波长、抽运光能量大小、入射的聚焦高斯光脉冲脉宽、相互作用时间等激光参数对SBS特征参数(Stokes散射光脉冲波形、材料内部最大应力的时间演化及空间分布、脉宽压缩效果、能量提取效率及Stokes散射光的共轭保真度)的影响.同时发现,SBS过程中产生的超声应力不仅会对SBS介质前表面造成破坏,还可能对焦点附近造成破坏;调整各激光参数还会使焦点附近优于前表面先破坏.数值模拟中采用的抽运光是聚焦高斯光束.

Numerical simulation was performed to study the stimulated Brillouin scattering(SBS) amplifier of self-Stokes-seeding. Chracteristic parameters such as Stokes laser, energy reflectivity, evolvement and distribution of maximum stress, pulse compression and SBS fidelity in fused silica were discussed for different Stokes ratio, wavelength, energy, pulse duration and interaction time. The focused Gaussian pump laser was used. We got conclusions that the damage in near-front side of SBS medium was the characteristic of SBS; tuning parameters of pump laser, super-sonic stress formed in SBS process would damage the SBS medium not only on the front side, but also the damage near the focus;and the damage near the focus would be made earlier when both parts were damaged.