基于主动种子匹配的百皮秒激光脉冲布里渊放大关键技术研究

Hundreds picosecond laser pulses with high peak power are the key to achieve inertial confinement nuclear fusion shock ignition,but direct amplification is inefficient. A method for high-efficiency hundreds picosecond laser pulse amplification by seed injection Stimulated Brillouin Scattering is proposed in this proposal. This method is inspired by the phenomena that pulse compression from nanosecond pump pulse to hundreds picosecond can be achieved through Stimulated Brillouin Scattering. However, the phase randomness of the acoustic field in self-excited SBS limits its applications. In this research, through frequency modulation , the phase of the acoustic field of in SBS is locked, the domain instability of Stokes pulse can be solved. Meanwhile, through the mechanism analysis of the SBS amplification, the interaction between the Stokes optical field with the acoustic field as well as the pump optical field is clarified, and then high efficiency energy transference is expected. The research is expected to provide an adaptable technology for amplification of hundreds picosecond pulses.

高峰值功率百皮秒激光脉冲是实现惯性约束核聚变（ICF）冲击点火的关键，然而直接放大效率较低。本项目提出了一种通过种子注入式受激布里渊散射实现高效百皮秒激光脉冲放大的方法。该想法的提出来自于受激布里渊散射（SBS）脉冲压缩技术可以将纳秒级的泵浦脉冲压缩至百皮秒级，然而，自激SBS过程中声波场的相位随机性限制了其应用的发展。本研究中，通过对SBS作用过程中Stokes种子光的频率调谐，实现SBS能量转移过程中声波场的相位锁定，解决Stokes脉冲时域不稳定的问题。同时，通过对种子注入式SBS放大过程物理机制的深入分析，阐述作用过程中Stokes脉冲在声波场以及泵浦光波场作用下的演变规律，实现能量的高效转移，为百皮秒激光脉冲SBS放大的应用发展提供技术支持。

本研究基于哈工大百焦耳装置开展了基于主动频率匹配受激布里渊散射能量转移的百皮秒激光放大研究。该技术方案主要通过在光纤前端系统插入基于声波控制的移频器，构建具有下频移的Stokes百皮秒种子脉冲，利用纳秒级的泵浦脉冲提取激光增益介质中的储能，最后在布里渊介质中将纳秒级的泵浦脉冲能量转移至Stokes百皮秒脉冲中，从而实现百皮秒激光脉冲的高效放大。基于非共线放大布里渊结构，在不同注入泵浦脉冲峰值功率的条件下可以实现10倍至40倍的Stokes百皮秒激光脉冲的峰值功率放大率，实现了百皮秒激光脉冲的高效放大。同时，通过对布里渊放大过程中瞬态增益的分析，通过瞬态增益的调节，突破了传统布里渊放大受限于介质声子寿命的理论，实现了脉冲宽度小于布里渊介质声子寿命的激光放大。